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1
Fan, Ji Wei, Xiao Peng Li, Zhen Guo Zhang, Zhi Qiang Jiao, Xiang Yang Liu, Wen Jing Zhang, Poonsuk Poosimma y Robert Freer. "The Effects of Cu Dopant on the Microstructure and Non-Ohmic Electrical Properties of ZnO Varistors". Advanced Materials Research 343-344 (septiembre de 2011): 160–65. http://dx.doi.org/10.4028/www.scientific.net/amr.343-344.160.
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The doping effects of Cu on the microstructure and non-ohmic electrical properties of ZnO varistors were studied. Addition of Cu2O can enhance the ZnO grain growth during sintering. The SEM and EDS results revealed that the added Cu mainly distributed in the grain boundary and spinel phases of ZnO varistors. The Cu2O addition increased the both of grain and grain boundary resistances. However it decreased the non-ohmic electrical characteristics of ZnO varistors, which is a good agreement with similar findings on Ag2O additions, but contrasts to the reports of good non-ohmic electrical property which found on binary Cu doped ZnO varistors.
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Zhou, Liqin y Changkui Yu. "Sintering and properties of low-firing non-ohmic SrTiO3 ceramics". Journal of Materials Science 29, n.º 22 (noviembre de 1994): 6055–59. http://dx.doi.org/10.1007/bf00366893.
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Peng, Chengxin, Bingxiang Zhao, Xie Meng, Xiaofeng Ye, Ting Luo, Xianshuang Xin y Zhaoyin Wen. "Effect of NiO Addition on the Sintering and Electrochemical Properties of BaCe0.55Zr0.35Y0.1O3-δ Proton-Conducting Ceramic Electrolyte". Membranes 14, n.º 3 (27 de febrero de 2024): 61. http://dx.doi.org/10.3390/membranes14030061.
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Proton ceramic fuel cells offer numerous advantages compared with conventional fuel cells. However, the practical implementation of these cells is hindered by the poor sintering activity of the electrolyte. Despite extensive research efforts to improve the sintering activity of BCZY, the systematic exploration of the utilization of NiO as a sintering additive remains insufficient. In this study, we developed a novel BaCe0.55Zr0.35Y0.1O3-δ (BCZY) electrolyte and systematically investigated the impact of adding different amounts of NiO on the sintering activity and electrochemical performance of BCZY. XRD results demonstrate that pure-phase BCZY can be obtained by sintering the material synthesized via solid-state reaction at 1400 °C for 10 h. SEM analysis revealed that the addition of NiO has positive effects on the densification and grain growth of BCZY, while significantly reducing the sintering temperature required for densification. Nearly fully densified BCZY ceramics can be obtained by adding 0.5 wt.% NiO and annealing at 1350 °C for 5 h. The addition of NiO exhibits positive effects on the densification and grain growth of BCZY, significantly reducing the sintering temperature required for densification. An anode-supported full cell using BCZY with 0.5 wt.% NiO as the electrolyte reveals a maximum power density of 690 mW cm−2 and an ohmic resistance of 0.189 Ω cm2 at 650 °C. Within 100 h of long-term testing, the recorded current density remained relatively stable, demonstrating excellent electrochemical performance.
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Ramírez, M. A., P. R. Bueno, E. Longo y J. A. Varela. "Conventional and microwave sintering of CaCu3Ti4O12/CaTiO3ceramic composites: non-ohmic and dielectric properties". Journal of Physics D: Applied Physics 41, n.º 15 (3 de julio de 2008): 152004. http://dx.doi.org/10.1088/0022-3727/41/15/152004.
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Nahm, Choon-W. "Sintering temperature dependence on microstructure and non-ohmic properties of ZVMND ceramic semiconductors". Journal of Materials Science: Materials in Electronics 27, n.º 9 (24 de mayo de 2016): 9520–25. http://dx.doi.org/10.1007/s10854-016-5003-6.
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El-Hofy, M. "Non-Ohmic Behavior of Some ZnO Ceramic Defective Ions with Different Valences". Defect and Diffusion Forum 293 (agosto de 2009): 91–97. http://dx.doi.org/10.4028/www.scientific.net/ddf.293.91.
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ZnO ceramic samples with the chemical formula, 97ZnO-2BaO-1(X)Mol% (where X= CuO, Fe2O3, TiO2, V2O5, MoO3) have been prepared by using conventional ceramics techniques. The samples were sintered at 1200°C for 1, 1.5 or 2h. The metal ions were chosen such that their ionic radii were just slightly different, whereas their ion valences varied from 2+ in case of Cu to 6+ for Mo. Room-temperature I-V characteristics, microstructures, linear scans and X-ray patterns were then studied. The microstructure and linear scan data revealed that, in the case of Cu-, Fe-, V- and Mo-doped ceramics, the doped ions resided mainly at the grain boundaries while, in case of Ti-doping, the ions resided mainly in the grain interior. The electrical measurements and the linear scan data showed that both the non-linearity parameter, α, and the rate of change of α with sintering time, (dα/dt), was exponentially proportional to the valence of the doped ion, where t is a sintering time in the range of 1 to 2h. The leakage current, JL, is linearly proportional to the amount of doped ion present in the grain interior, relative to that present at the boundaries. The X-ray data revealed that the obtained phase was the hexagonal ZnO phase, with traces of secondary phase related to the doped ion; the secondary phases were identified as being Fe2O3, BaTi5O11, Zn3(VO4)2 and (ZnMoO4) in case of Fe-, Ti-, V- and Mo-doped ceramics, respectively. The relative intensity of the X-ray peak at 2θ = 34.45, corresponding to the (0002) plane, was exponentially proportional to the valence of the doped ion; while α scaled with the relative intensity of the aforementioned X-ray peak.
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Galizia, Pietro y Carmen Galassi. "Electrophoretic Deposition of Bilayer Based on Sacrificial Titanium Dioxide and Lead Zirconate Titanate on Bare Silicon Wafer". Key Engineering Materials 654 (julio de 2015): 132–35. http://dx.doi.org/10.4028/www.scientific.net/kem.654.132.
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Bilayer thick films of sacrificial titanium dioxide and Nb-doped lead zirconate titanate (PZTN) have been deposited on bare silicon wafers using electrophoretic deposition (EPD) technique. Deposition of such ceramic particles, dispersed ethanol-based suspensions, on semiconductor substrate has been made possible after preparation of alloyed junctions Al/Si characterized by ohmic behaviour. Sintering of green TiO2/PZTN films was performed at 900 °C for 1 h. The composition of the films, the thickness and relative density of the deposited materials have been analysed by EDS-SEM analysis. The lead diffusion through the silicon wafer has been reduced.
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Dubey, Pawan Kumar Kumar, Junsung Hong, Kevin X. Lee, Seraphim Belko, Ashish Aphale, Muhammad Anisur Rahman, Michael Reisert y Prabhakar Singh. "Electrical Conductivity and Electrochemical Performance of Pr Doped Ceria". ECS Transactions 111, n.º 6 (19 de mayo de 2023): 91–103. http://dx.doi.org/10.1149/11106.0091ecst.
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PCO (Praseodymium Cerium Oxide) solid solution (0-50% PrOx) has been prepared by the conventional solid-state ceramic processing route using CeO2 and PrOx powders in the desired stoichiometry and sintering at 1500°C in air. Synthesized powder has been characterized for phase chemistry and lattice structure. Electrochemical characteristics of the synthesized powder has been examined using electrochemical impedance spectroscopy. The observed increase in the electrical conductivity of PCO are associated with increased concentration of oxygen vacancies created by the replacement of Ce4+ ions with Pr+3 ions. The addition of PrOx also lowered the polarization and ohmic losses.
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Liu, Huan, Rong Zhu, Zhi Ping Zheng, Dong Xiang Zhou y Qiu Yun Fu. "Effect of Ni Electrode on the Characteristics of BaTiO3 Based PTCR Ceramics". Advanced Materials Research 415-417 (diciembre de 2011): 1000–1004. http://dx.doi.org/10.4028/www.scientific.net/amr.415-417.1000.
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In order to achieve cost-effective inner electrodes for the multilayer BaTiO3-based ceramics having a positive temperature coefficient of resistivity (PTCR), we fabricated Ni paste based on Ni powder and investigated the effect of Ni electrode on the performance of semiconducting BaTiO3 ceramics. We adjusted the particle size of Ni powder (0.2μm, 0.6μm and 1μm) and incorporated them as the electrodes into both single-layer and laminated BaTiO3 PTCR devices. The device samples were sintered at 1200oC for 30min in reducing atmosphere consisting of N2 and H2 (97:3 by volume ratio), and went through a post-sintering in-air heat treatment at 700-900oC in air which is necessary for the PTCR effect. The results indicate that Ni powder with lager particle size are more stable against post-sintering heat treatment, and the heating temperature needs to be optimized to overcome the trade-off between ohmic behaviors of Ni electrodes and the PTCR effect of BaTiO3-based semiconducting ceramics.
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Su, Yan Kuin, Fuh Shyang Juang y Kuang Jou Gan. "Ohmic Contacts of AuGeNi and Ag/AuGeNi to n-GaSb with Various Sintering Temperatures". Japanese Journal of Applied Physics 30, Part 1, No. 5 (15 de mayo de 1991): 914–16. http://dx.doi.org/10.1143/jjap.30.914.
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Mielcarek, Witold, Slavko Bernik y Krystyna Prociów. "Relations between the Morphology of ZnO Powders and the Electrical Performance of ZnO Varistors". Key Engineering Materials 336-338 (abril de 2007): 672–75. http://dx.doi.org/10.4028/www.scientific.net/kem.336-338.672.
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Because of their unusual properties – non-ohmic behavior and the ability to absorb a lot of energy – metal-oxide varistors are widely used for the protection of electrical and electronic devices against over-voltages. ZnO ceramics have varistor properties because of their metal-oxide additives and the microstructures developed during sintering. The value of the varistor voltage depends largely on the number of conducting ZnO grains between the electrodes; this can be set by controlling the thickness of the device or the size of the grains. The desired grain size can be achieved by altering the composition of the metal-oxide additives and the sintering conditions. In this work the grain growth was controlled by combining two ZnO powders of differing sinterability in the starting material. Also, the use of BaBiO2.77 as a precursor for Bi2O3 is an innovation in varistor technology that makes it possible to reduce the amount of added metal oxides. As a result, a variety of varistors with good varistor properties and a wide range of working parameters were produced.
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Muhoza, Sixbert P. y Michael D. Gross. "Creating and Preserving Nanoparticles during Co-Sintering of Solid Oxide Electrodes and Its Impact on Electrocatalytic Activity". Catalysts 11, n.º 9 (6 de septiembre de 2021): 1073. http://dx.doi.org/10.3390/catal11091073.
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A novel processing method that creates and preserves ceramic nanoparticles in solid oxide electrodes during co-sintering at traditional sintering temperatures is introduced. Specifically, carbon templated samarium-doped ceria nanoparticles (nSDC) were successfully integrated with commercial lanthanum strontium cobalt ferrite (LSCF) and commercial SDC powders, producing LSCF-SDC-nSDC cathodes upon processing. The effect of nSDC concentration on cathode electrocatalytic activity was investigated at low operational temperatures, 600 °C–700 °C, with symmetrical cells. Low nSDC loadings, ≤5 wt% nSDC, significantly decreased cell polarization resistance whereas higher loadings increased it. The best electrochemical performance was achieved with 5 wt% nSDC, lowering the polarization resistance by 41% at 600 °C. Fuel cell tests demonstrate that adding 5 wt% nSDC increased the maximum fuel cell power density by 38%. Electrochemical impedance spectra showed substantial improvements in both fuel cell polarization resistance and ohmic resistance, indicating that nSDC increased the electrocatalytically active area of the cathode. This work demonstrates a simple, novel method for effectively increasing electrocatalytic activity of solid oxide electrodes at low operational temperatures.
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Schmitz, K. M., K. L. Jiao, R. Sharma, W. A. Anderson, G. Rajeswaran, L. R. Zheng, M. W. Cole y R. T. Lareau. "Microstructural analysis of Pd-based ohmic contacts to p-type GaAs". Journal of Materials Research 6, n.º 3 (marzo de 1991): 553–59. http://dx.doi.org/10.1557/jmr.1991.0553.
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As part of the investigation of the use of Pd-based ohmic contacts to p-type GaAs, cross-sectional transmission electron microscopy, Auger electron spectroscopy, and secondary ion mass spectroscopy were used to explore the uniformity at the metal/GaAs interface and its composition profile after ohmic contact formation. Comparisons were made among Au:Be, Au:Be/Pd, and Au/Pd contacts. Regions of p+ were formed in n-type GaAs by a spin-on source which was rapid diffused at 950 °C for 6 s or by ion implantation at a dose of 3 × 1014 atoms/cm2 at 150 keV for 15 min. Metallizations were accomplished by evaporation with a base pressure of 3 × 10−6 Torr. Sintering of the metallizations was done in a furnace at 350 °C for 15 min. Cross-sectional transmission electron microscope studies revealed an absence of spiking when Be is present in the metallization scheme but a broad band diffused into GaAs. An improper metal/GaAs adhesion was observed when Pd is absent. Be assists in confining the reaction of Pd with GaAs and acts as a diffusion barrier to the p+ dopant. Electrical measurements, taken from transmission line and cross bridge Kelvin resistors, were best for the Pd/Au:Be, which yielded a contact resistance of 0.3 μΩ-cm2.
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Hara, Masahiro, Takeaki Kitawaki, Kotaro Kuwahara, Hajime Tanaka, Mitsuaki Kaneko y Tsunenobu Kimoto. "(Invited) Tunneling Phenomena and Ohmic Contact Formation at Non-Alloyed Metal/Heavily-Doped SiC Interfaces". ECS Meeting Abstracts MA2024-02, n.º 36 (22 de noviembre de 2024): 2520. https://doi.org/10.1149/ma2024-02362520mtgabs.
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To clarify the formation mechanism of alloyed ohmic contacts on SiC by high-temperature sintering (~1000°C) and to improve the fabrication process of SiC electronic devices, a physical understanding of fundamental properties at non-sintered (non-alloyed) metal/heavily-doped SiC interfaces is indispensable. This paper reviews tunneling phenomena through a thin Schottky barrier at non-alloyed contacts on heavily-doped SiC, and design guidelines toward low-resistance ohmic contacts are proposed based on transport modeling. The first target was a Schottky contact formed on a heavily nitrogen-doped n-type SiC epitaxial layer. Vertical Schottky barrier diode (SBD) structures were fabricated by systematically varying the donor density in the epitaxial layers (up to 1019 cm−3), and the current-voltage (I-V) characteristics were analyzed based on a numerical calculation of direct tunneling (DT) current, in which energy integration of carrier distribution and tunneling probability is performed. Note that the DT transport describes both the thermionic field emission (TFE) and field emission (FE). The numerical calculation reproduces well the experimental I-V curves for vast ranges of the donor density, barrier height, and applied voltage. The authors also formed Schottky contacts on heavily aluminum-doped p-type SiC epitaxial layers and revealed unique DT transport associated with the complicated valence band structure of SiC. The valence band in SiC has a split-off band with a light effective mass (m * = 0.2m 0), which is located at the energy of several tens of meV above the topmost heavy- and light-hole bands (m * = 1.6m 0). Reflecting the exponential contribution of the effective mass to the tunneling probability, carrier transport through non-alloyed contacts on heavily-doped p-type epitaxial layers is dominated by hole tunneling through the split-off band. The next step was to clarify how different the interface properties are between the cases of epitaxial and ion-implanted layers. It was found that vertical SBDs fabricated with heavily phosphorus- and aluminum-implanted n- and p-type SiC, respectively, both exhibit several orders of magnitude larger current than those with epitaxial layers having almost identical doping densities. Systematic analysis of the Schottky barrier height through capacitance-voltage (C-V) measurement revealed that there is no significant difference in the barrier height at the contacts on ion-implanted and epitaxial layers, indicating a contribution of a carrier transport process other than DT. The enhanced current is likely explained by trap-assisted tunneling (TAT) through implantation-induced deep levels. Toward modeling of contact resistivity based on the deep understanding of the tunneling phenomena (DT and TAT) gained above, experimental characterization and numerical analysis of the contact resistivity at non-alloyed ohmic contacts formed on heavily ion-implanted n- and p-type SiC were performed. At non-sintered Mg and Ti contacts on n-type SiC (donor density: 2×1020 cm−3), corresponding to the barrier height of 0.7 and 1.0 eV, respectively, an extremely low contact resistivity of 1-2×10−7 Ωcm2 was achieved without performing any thermal treatment after the electrode formation. As for p-type SiC with the acceptor density of about 1×1020 cm−3, a Ni contact (barrier height: 1.7 eV) exhibited a relatively low contact resistivity of 9.8×10−3 Ωcm2 without sintering. Through comparison between the contact resistivities experimentally and numerically obtained, how the dominant tunneling process changes depending on the doping density is carefully discussed, and a physics-based model considering the contributions of DT and TAT to predict the contact resistivity at non-alloyed ohmic contacts on implanted SiC is proposed as follows: the contact resistivity is significantly reduced thanks to a contribution of the TAT when the doping density is below about 1020 cm−3, and the contact resistivity at further high doping density sharply decreases and is well predictable based on the DT theory. The proposed model provided several quantitative guidelines regarding the doping density and barrier height for designing low-resistance ohmic contacts on SiC. The model to predict the contact resistivity standing on the physics of tunneling is beneficial not only for a deeper understanding of the ohmic contact formation on SiC but also for exploring a novel low-temperature fabrication process toward low-resistance ohmic contacts. Besides, the high-field tunneling phenomena revealed in this study are expected to be commonly observed at contacts formed on other wide-bandgap semiconductors. Thus, the present data and model can also give a critical insight into the ohmic contact formation on these materials.
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Oliveira, M. M., P. R. Bueno, M. R. Cassia-Santos, E. Longo y J. A. Varela. "Sensitivity of SnO2 non-ohmic behavior to the sintering process and to the addition of La2O3". Journal of the European Ceramic Society 21, n.º 9 (septiembre de 2001): 1179–85. http://dx.doi.org/10.1016/s0955-2219(00)00329-0.
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Chong, Haining, Huijun Yang, Weiyou Yang, Jinju Zheng, Minghui Shang, Zuobao Yang, Guodong Wei y Fengmei Gao. "SiC Nanowire Film Photodetectors: A Promising Candidate Toward High Temperature Photodetectors". Journal of Nanoscience and Nanotechnology 16, n.º 4 (1 de abril de 2016): 3796–801. http://dx.doi.org/10.1166/jnn.2016.11875.
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In this study, UV photodetectors (PDs) based on SiC nanowire films have been successfully prepared by a simple and low-cost drip-coating method followed by sintering at 500 °C. The corresponding electrical characterizations clearly demonstrate that the SiC nanowire based PD devices can be regarded as a promising candidate for UV PDs. The PDs can exhibit the excellent performances of fast, high sensitivity, linearity, and stable response, which can thus achieve on-line monitoring of weak UV light. Furthermore, the SiC nanowire-based PDs enable us to fabricate detectors working under high temperature as high as 150 °C. The high photosensitivity and rapid photoresponse for the PDs can be attributed to the superior single crystalline quality of SiC nanowires and the ohmic contact between the electrodes and nanowires.
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Sahu, Rashmirekha y Pawan Kumar. "Microstructure and electrical properties of microwave sintered Nb-doped NBT ceramics". Processing and Application of Ceramics 15, n.º 4 (2021): 395–402. http://dx.doi.org/10.2298/pac2104395s.
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Nb5+-doped sodium bismuth titanate (NBT) ceramics ((Na0.5Bi0.5)1-x/2Ti1-xNbxO3 where x = 0, 0.005, 0.01 and 0.015) were obtained by microwave assisted solid state reaction route and microwave sintered at 1000 ?C. Microwave processing technique was chosen for the sintering as it is a powerfulmethod which enables sintering in a short time with fast heating rate avoiding grain growth. The influence of Nb5+-doping on microstructure and electrical properties of the NBT ceramics was studied. X-ray diffraction analyses revealed that solubility limit of niobium in NBT lattice is up to 1mol%, as with further increase in niobium concentration pyrochlore appeared. Microstructure of all the ceramics was investigated by field emission scanning electron microscopy and it was observed that the average grain size decreased with doping. Temperature dependent dielectric study was carried out for all the ceramics at different frequency. All ceramics show diffusive dielectric behaviour around Tm and introduction of Nb even increases compositional fluctuation compared to the parent NBT. Nb-doping shifts the Tm toward lower temperature. Leakage current study showed that for whole range of electric field ohmic type conduction mechanism is dominant for all the ceramics. Room temperature polarization-electric field (P-E) hysteresis loop confirms the ferroelectric behaviour of all the ceramics.
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Hossein-Babaei, Faramarz y S. Masoumi. "Electrical Resistance and Seebeck Effect in Undoped Polycrystalline Zinc Oxide". Key Engineering Materials 605 (abril de 2014): 185–88. http://dx.doi.org/10.4028/www.scientific.net/kem.605.185.
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Thermoelectric properties of metal oxide semiconductors are of increasing interest in the field of sensors design and fabrication. The oxide components in the majority of such applications are polycrystalline in which the charge transportation is controlled both by the microstructure and the bulk properties of the material. While the dependence of the electrical resistivity on the microstructural and compositional changes in these materials is well understood, the complications encountered with their thermoelectric properties, have remained unattended. Here, we report experimental data on the Seebeck coefficient of undoped polycrystalline zinc oxide measured on the ceramic pellets fabricated by dry pressing of the powder and sintering at 800 and 1000°C, in air. Aluminum ohmic contacts are used for electrical connections. Seebeck voltage and electrical resistivity are measured at various temperatures and different atmospheric condition at the presence of predetermined temperature gradients.
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Klitkou, Morten Phan, Albert Lopez de Moragas, Julian Taubmann, Peyman Khajavi, Stéven Pirou, Henrik Lund Frandsen y Peter Vang Hendriksen. "Development of Fuel Electrode Supported Solid Oxide Cell with Ni/CGO Active Layer". ECS Transactions 111, n.º 6 (19 de mayo de 2023): 1407–13. http://dx.doi.org/10.1149/11106.1407ecst.
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A half-cell comprising of a Ni/3YSZ support, a Ni/CGO10 active fuel electrode, a thin ScYSZ electrolyte and a CGO10 barrier layer was realized through tape casting, lamination and co-sintering. After screen printing of air electrode and contact layer, the cell was electrochemically tested using EIS at open circuit voltage. At 750°C in 50/50 H2O/H2 ohmic resistance (Rs) was encouraging at 0.18 Ω.cm2. Polarization resistance (Rp) was however significantly larger than state of the art (SoA) cells at 0.45 Ω.cm2. From electrochemical analysis the causes for the large Rp are hypothesized to be poor air electrode performance and low fuel electrode performance. This transaction paper includes a description of ongoing activities to improve the electrochemical performance of this cell concept to approach or surpass SoA fuel electrode supported solid oxide cells (FE-SOC) relying on Ni/YSZ electrodes.
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Kim, Junseok, Sahn Nahm, Jong-Ho Lee y Ho-il Ji. "A Simple Preparation of Electrolyte Powder for Stoichiometric Electrolyte in Protonic Ceramic Cells". ECS Meeting Abstracts MA2023-01, n.º 54 (28 de agosto de 2023): 283. http://dx.doi.org/10.1149/ma2023-0154283mtgabs.
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Among various eco-friendly energy conversion technologies, solid oxide cells (SOCs) exhibit superior energy conversion efficiency and performance owing to the kinetic and thermodynamic advantages. Recently, protonic ceramic cells (PCCs) have begun to attract attention with expectation that the operating temperature of SOCs can be lowered around 500oC, thereby achieving better durability with maintaining higher conversion efficiency. However, the promising proton conducting electrolytes in PCCs are mostly Ba-containing perovskites exhibiting highly refractory property, thus substantially have challenges associated with barium volatilization during high-temperature sintering process. At the same time, Ni-containing transient phases generated at the electrode and supplied to the electrolyte during sintering of electrode/electrolyte bilayer not only facilitate the sintering of electrolyte, but also induce the compositional change owing to the residue thereof. Such off-stoichiometry indeed degrades the electrical properties, and thus most of all reported performance of PCCs could not fully reflect the intrinsic property of electrolytes. Here, we describe a simple but effective strategy to realize the highly conductive electrolyte in PCCs via suppression of barium volatilization as well as minimization of supplied amount of transient phases; a low-temperature calcination process. The electrolyte powder calcined at the relatively lower temperature, which is high enough to react all the precursors without residue, but low enough to suppress the Ba volatilization. The PCCs fabricated using this low-temperature calcined electrolyte powder shows the reduced ohmic resistance, and in turn, enhanced electrochemical performance. While the research on PCCs, up to now, have mainly been focused on processing technique or new materials for the better performance, the result of this study implies that the status of initial electrolyte powder can significantly influence the overall cell characteristics.
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Nahm, Choon-Woo. "Non-ohmic properties and impulse aging behavior of quaternary ZnO–V2O5–Mn3O4–Er2O3 semiconducting varistors with sintering processing". Materials Science in Semiconductor Processing 16, n.º 5 (octubre de 2013): 1308–15. http://dx.doi.org/10.1016/j.mssp.2013.04.003.
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Umamakeshvari, K. y S. C. Vella Durai. "A study of dielectrics generated by electro-less electrochemical method for semiconductor devices". Journal of Ovonic Research 18, n.º 2 (abril de 2022): 281–90. http://dx.doi.org/10.15251/jor.2022.182.281.
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The aim of this work is to the basic concepts of the varies chemical and electrochemical procedures used m the fabrication of semiconductor devices seems to be useful to provide a suitable background for the present work, a brief review of the same as also the results obtained by earlier workers has been undertaken at the outset. A careful scrutiny of the results obtained by different workers reveals that although the aforesaid methods have a few limitations, they may be satisfice borily used as an alternative to sputter and evaporation techniques for device fabrication. The author carried out experimental investigations on the formation and properties of ohmic contact to silicon using two electroless plating baths - one operated at room temperature and the other at 95°C. In particular, the variation of contact resistance of ohmic contacts formed by electroless Ni-P process on silicon was studied as a function of sintering temperatures with operating point temperatures and pH of the baths as parameters. ^rom these studies it has been shown that both the baths yielded an adherent and dense deposit of nickel-phosphorous alloy on n-Si, which when sintered at very high temperatures give a less value of contact resistance due to the formation of metal-n -n contact. The phosphorous component of the Ni-P deposit diffuses into n-Si during heat treatment and forms the metal-n+ --n contact which behaves as an ohmic contact. As expected, the value of contact resistance was found to decrease with the increase of phosphorous materials in the deposit. The most favourable temperature range of heat treatment was found to be between 600°-700°C. Heats studying above 700°C slightly less increase the contact resistance probably due to the out diffusion of phosphorous from the Ni-P deposit. The barrier height and ideality factor are two important parameters for m-s contacts. The values of these two parameters of electrochemically fabricated Schottky diodes as obtained from the capacitance and current voltage characteristics were found to be in fairly close agreement with those of vacuumevaporated diodes. It is therefore, concluded that the electrochemical method of metal deposition is a valid and convenient technique for the fabrication and study of metalsemiconductor contacts
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Nahm, Choon-W. "Non-ohmic effect and pulse aging behavior of V/Mn/Co/Bi/Dy co-doped ZnO semiconducting varistors with sintering processing". Materials Science in Semiconductor Processing 26 (octubre de 2014): 455–59. http://dx.doi.org/10.1016/j.mssp.2014.04.035.
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Miranda López, M. I., M. B. Hernández Hernández, B. S. Vera Barrios, A. Toxqui Teran y J. A. Aguilar Martinez. "A comparative study between the addition of nano and micro-particles of Co3O4 on the electrical and microstructural properties of a ceramic system based on SnO2". Revista Mexicana de Física 66, n.º 1 (28 de diciembre de 2019): 47. http://dx.doi.org/10.31349/revmexfis.66.47.
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A comparative study between the addition of Co3O4 micro-particles and nano-particles as densifying dopant of a SnO2 based varistor system was conducted. The ceramic composition was (99.9-X) %SnO2–X %Co3O4–0.05 %Cr2O3–0.05 %Nb2O5 where X = 0, 0.5, 1.0, 2.0 and 4.0 mol%. Two particle sizes of Co3O4 were used (~5 µm and ~50 nm). The addition of 0.5 mol% of Co3O4 nano-particles promoted an increase of grain size of sintered samples up to 7.9 µm, that is, the maximum value among all variations. Characterization techniques such as TGA, DTA, XRD, and Rietveld analysis revealed a decrease of 16 ºC in the formation temperature of Co2SnO4 as well as an increase of 2.6 wt% in the amount of said phase with the use of 4.0 mol% of Co3O4 nano-particles in comparison with micro-particles. Statistical analysis indicated that the addition of nano-particles of Co3O4 yield better repeatability on densification of ceramic samples. Residual porosity also was decreased. Electrical breakdown and non-linear coefficient values correspond to a non-ohmic behavior with potential application on manufacture of high voltage varistors. The findings of this work can be used as a reference for conducting a later study to improve the electrical properties or even to lower the sintering temperature.
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Dzunuzovic, Adis, Mirjana Vijatovic-Petrovic, Nikola Ilic, Jelena Bobic y Biljana Stojanovic. "Magneto-dielectric properties of ferrites and ferrite/ferroelectric multiferroic composites". Processing and Application of Ceramics 13, n.º 1 (2019): 104–13. http://dx.doi.org/10.2298/pac1901104d.
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Ni-Zn ferrites, with the general formula Ni1-xZnxFe2O4 (x = 0.0, 0.3, 0.5, 0.7, 1.0), CoFe2O4, BaTiO3 and PbZr0.52Ti0.48O3 powders were synthesized by auto-combustion method. The composites were prepared by mixing the appropriate amounts of individual phases, pressing and conventional sintering. X-ray analysis, for individual phase and composites, indicated the formation of crystallized structure of NiZnFe2O4, BaTiO3 and PbZr0.52Ti0.48O3 without the presence of secondary phases or any impurities. SEM analyses indicated a formation of uniform grain distribution for ferromagnetic and ferroelectric phases and formation of two types of grains, polygonal and rounded, respectively. Magneto-dielectric effect was exhibited in all samples because of the applied stress occurring due to the piezomagnetic effect and the magnetic field induced the variation of the dielectric constant. For all samples the dielectric constant was higher in applied magnetic field. At the low frequency, the dispersion of dielectric losses appeared, while at the higher frequency the value of tan ? become constant (Maxwell-Wagner relaxation). Investigation of J-E relation between leakage and electric field revealed that both nickel zinc ferrite and composites have three different regions of conduction: region with ohmic conduction mechanism, region with the trap-controlled space charge limited current mechanism and region with space charge limited current mechanism.
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Tarutin, Artem, Julia Lyagaeva, Andrey Farlenkov, Sergey Plaksin, Gennady Vdovin, Anatoly Demin y Dmitry Medvedev. "A Reversible Protonic Ceramic Cell with Symmetrically Designed Pr2NiO4+δ-Based Electrodes: Fabrication and Electrochemical Features". Materials 12, n.º 1 (31 de diciembre de 2018): 118. http://dx.doi.org/10.3390/ma12010118.
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Reversible protonic ceramic cells (rPCCs) combine two different operation regimes, fuel cell and electrolysis cell modes, which allow reversible chemical-to-electrical energy conversion at reduced temperatures with high efficiency and performance. Here we present novel technological and materials science approaches, enabling a rPCC with symmetrical functional electrodes to be prepared using a single sintering step. The response of the cell fabricated on the basis of P–N–BCZD|BCZD|PBN–BCZD (where BCZD = BaCe0.5Zr0.3Dy0.2O3−δ, PBN = Pr1.9Ba0.1NiO4+δ, P = Pr2O3, N = Ni) is studied at different temperatures and water vapor partial pressures (pH2O) by means of volt-ampere measurements, electrochemical impedance spectroscopy and distribution of relaxation times analyses. The obtained results demonstrate that symmetrical electrodes exhibit classical mixed-ionic/electronic conducting behavior with no hydration capability at 750 °C; therefore, increasing the pH2O values in both reducing and oxidizing atmospheres leads to some deterioration of their electrochemical activity. At the same time, the electrolytic properties of the BCZD membrane are improved, positively affecting the rPCC’s efficiency. The electrolysis cell mode of the rPCC is found to be more appropriate than the fuel cell mode under highly humidified atmospheres, since its improved performance is determined by the ohmic resistance, which decreases with pH2O increasing.
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Watanabe, Konosuke, Hiroyuki Shimada, Aman Sharma, Masaya Fujioka, Yuki Yamaguchi, Katsuhiro Nomura, Hirofumi Sumi y Yasunobu Mizutani. "(Invited) Investigation of Co-Free Cathode Composited with Proton Conductors for Protonic Ceramic Fuel Cells with Yb-Doped BaZrO3 Electrolyte". ECS Meeting Abstracts MA2024-02, n.º 48 (22 de noviembre de 2024): 3323. https://doi.org/10.1149/ma2024-02483323mtgabs.
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Protonic ceramic fuel cells (PCFCs) are expected to gain significant advantage from the use of Co-free cathodes. This shift can lead to reduced manufacturing costs and enhance durability performance. In our previous study, the investigation compared the power generation characteristics of PCFCs with BaZr0.8Yb0.2O3-δ (BZYb) electrolytes utilizing cathodes composed of La0.6Sr0.4FeO3-δ (LSF) as a Co-free cathode material and La0.6Sr0.4CoO3-δ (LSC) or La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) as Co-containing cathode materials composited with BZYb. Consequently, the PCFC with an LSF-BZYb cathode exhibited lower performance compared to the PCFCs with LSC-BZYb and LSCF-BZYb cathodes due to the higher electrode polarization resistance. In this study, the challenges associated with achieving high-performance Co-free cathodes that can match the performance of Co-containing cathodes are presented, along with the mechanism to enhance performance. To improve performance, the use of La0.65Ca0.35FeO3-δ (LCaF), as a Co-free cathode, in addition to LSF, which has been reported to demonstrate high performance in SOFCs, was explored. Additionally, LCaF was composited with BaCe0.7Zr0.1Y0.1Yb0.1O3-δ (BCZYYb), known for its higher proton conductivity and easier sinterability than BZYb. When comparing the power generation characteristics of PCFCs with LCaF-BZYb and LSF-BZYb cathodes, the PCFC with LCaF-BZYb cathode exhibited higher ohmic and electrode polarization resistances. These results were attributed to weak adhesion between the electrolyte and cathode, resulting in lower performance than the PCFC with LSF-BZYb cathode. Furthermore, when comparing the power generation characteristic of the PCFC with a composite cathode of LCaF and BCZYYb with the LCaF-BZYb cathode, the ohmic and electrode polarization resistances were significantly lower. This improvement was attributed to the advanced sintering of BCZYYb and the connected percolation of the proton-conducting network. Consequently, the performance of the PCFC with the LCaF-BCZYYb cathode surpassed that of the LCaF-BZYb cathode and was comparable to Co-containing cathodes such as LSC-BCZYYb cathode. In conclusion, for Co-free cathodes in PCFCs, it is crucial to composite them with proton conductors possessing better sinterability, such as BCZYYb, to achieve higher performance. Acknowledgements: This work is based on the results obtained from a project (JPNP20003) commissioned by the New Energy and Industrial Technology Development Organization (NEDO), Japan.
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Adjah-Tetteh, Christabel, Yudong Wang, Zizhou He, Nengneng Xu y Xiao-Dong Zhou. "A Novel Process to Achieve Enhanced Mechanical and Electrical Properties of (Mn,Co)3O4-Based Electrical Contact Layer for Solid Oxide Cells". ECS Meeting Abstracts MA2024-02, n.º 67 (22 de noviembre de 2024): 4653. https://doi.org/10.1149/ma2024-02674653mtgabs.
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To reduce ohmic losses and increase power output in an SOFC stack, electrical contact materials have been employed between the interconnect and oxide cathode. One of the possible candidate materials for the electrical contact layer is (Mn, Co)3O4, which is also used as the interconnect coating in an SOFC stack, due largely to its coefficient of thermal expansion that matches with the interconnect and cathode [1, 2]. The (Mn, Co)3O4 is electrically conducting, yet its conductivity remains several orders of magnitude lower than certain perovskite counterparts, such as (La, Sr)CoO3. In addition, (Mn, Co)3O4 often requires high sintering temperature (≥ 1000°C) when the oxide powders are used as starting materials [1, 3]. There is a need to develop novel processes to reduce the sintering temperature of (Mn, Co)3O4 to about 850°C, at which the sealing glass is sintered. In this work, we employ a new approach to fabricate (Mn, Co)3O4 spinels as the electrical contact materials. This innovation significantly enhanced the conductance of the contact layer and its bonding strength. The bonding strength with interconnect is evaluated by evaluating the maximum shear stress when the spinel layer is sandwiched by two 430 stainless steel coupons. Electrical resistance is measured for the contact layer with different Mn-Co ratios. References [1] J. H. Zhu and H. Ghezel-Ayagh, "Cathode-side electrical contact and contact materials for solid oxide fuel cell stacking: A review," International Journal of Hydrogen Energy, vol. 42, no. 38, pp. 24278-24300, 2017. [2] Z. Yang, G. Xia, and J. W. Stevenson, "Mn1. 5Co1. 5 O 4 spinel protection layers on ferritic stainless steels for SOFC interconnect applications," Electrochemical and Solid-State Letters, vol. 8, no. 3, p. A168, 2005. [3] A. Petric and H. Ling, "Electrical conductivity and thermal expansion of spinels at elevated temperatures," Journal of the American Ceramic Society, vol. 90, no. 5, pp. 1515-1520, 2007.
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Lee, Wonyoung, Mingi Choi, Jaedeok Paik, Deokyoon Woo, Jaeyeob Lee, Seo Ju Kim y Jongseo Lee. "(Invited) Highly Performing Protonic Ceramic Fuel Cells with Stoichiometric Electrolytes". ECS Meeting Abstracts MA2022-02, n.º 47 (9 de octubre de 2022): 1736. http://dx.doi.org/10.1149/ma2022-02471736mtgabs.
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Among various types of solid oxide electrochemical cells, protonic ceramic fuel cells (PCFCs) have been expected to reduce the operating temperature below 600 °C with their significantly high ionic conductivity and activation energy. For example, recently developed proton conductor (BaZr0.4Ce0.4Y0.1Yb0.1O3-δ, BZCYYb) ideally has ~12-fold higher ionic conductivity (2.810-2 S/cm at 600 °C) and low activation energy (Ea < 0.4 eV) than those of conventional oxide ion conductor (Y0.08Zr0.92O2-δ; 2.810-3 S/cm at 600 °C and Ea ~0.87 eV). However, the low chemical and physical stabilities of proton conducting oxides during fabrication processes, primarily due to the high mobility and volatility of Barium (Ba), induce the substantially lower electrochemical performance than their predictions, limiting their utilization and application. Here, we present the chemically and physically stable BZCYYb electrolyte with the desired stoichiometry and the average grain size of ~10 µm by controlling the chemical potential of the A-site cation, Ba, near the BZCYYb electrolyte surface during the sintering process. A stoichiometric BZCYYb-based PCFC in an anode-supported configuration exhibits 1.90/cm2 and 1.01 W/cm2 with an extremely low ohmic resistance of ~0.060 ohm·cm2 at 650 °C and ~0.082 ohm·cm2 at 550 °C, respectively, surpassing the values of all previously reported PCFCs without complicated engineering in materials and structures of other cell components.
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Choi, Mingi. "Protonic Ceramic Fuel Cells with Stoichiometric Electrolytes". ECS Meeting Abstracts MA2023-01, n.º 54 (28 de agosto de 2023): 271. http://dx.doi.org/10.1149/ma2023-0154271mtgabs.
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Among various types of solid oxide electrochemical cells, protonic ceramic fuel cells (PCFCs) have been expected to reduce the operating temperature below 600 °C with their significantly high ionic conductivity and activation energy. For example, recently developed proton conductor (BaZr0.4Ce0.4Y0.1Yb0.1O3-δ, BZCYYb) ideally has ~12-fold higher ionic conductivity (2.810-2 S/cm at 600 °C) and low activation energy (Ea < 0.4 eV) than those of conventional oxide ion conductor (Y0.08Zr0.92O2-δ; 2.810-3 S/cm at 600 °C and Ea ~0.87 eV). However, the low chemical and physical stabilities of proton conducting oxides during fabrication processes, primarily due to the high mobility and volatility of Barium (Ba), induce the substantially lower electrochemical performance than their predictions, limiting their utilization and application. Here, we present the chemically and physically stable BZCYYb electrolyte with the desired stoichiometry and the average grain size of ~10 µm by controlling the chemical potential of the A-site cation, Ba, near the BZCYYb electrolyte surface during the sintering process. A stoichiometric BZCYYb-based PCFC in an anode-supported configuration exhibits 1.90/cm2 and 1.01 W/cm2 with an extremely low ohmic resistance of ~0.060 ohm·cm2 at 650 °C and ~0.082 ohm·cm2 at 550 °C, respectively. Our results may open the possibility of finding a technical breakthrough for various next-generation electrochemical systems having desirable material properties without the requirement for complicated and expensive fabrication processes.
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Won, Bo-Ram, Yo Han Kim, Hyeongwon Jeong, Dayoung Park y Jae-Ha Myung. "Highly Bendable Solid Oxide Fuel Cells Via Phase Control of Zirconia-Based Electrolyte". ECS Meeting Abstracts MA2024-02, n.º 48 (22 de noviembre de 2024): 3466. https://doi.org/10.1149/ma2024-02483466mtgabs.
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Despite numerous studies, conventional solid oxide fuel cells (SOFCs) face limitations in commercialization due to the vulnerability of brittle ceramic materials to external stress. To address this issue, we propose a structural approach to design the support with excellent energy absorption capability using a flexible ceramic. In this study, we introduce a next-generation concept of highly flexible SOFCs with a bendable zirconia-based electrolyte, aiming to enhance mechanical stability and ensure long-term operation. The mechanical flexibility of the electrolytes is achieved by controlling the crystal structure within the range corresponding to a transformable tetragonal phase (with a tetragonality range of c/a > 1.010). Furthermore, we adjust the mechanical strength and ionic conductivity by varying the tetragonal phase fraction depending on sintering temperatures. Finally, the optimized electrolyte demonstrates superior bending strength and ohmic resistance properties, enabling it to withstand severe deformations such as folding. Based on experimental results, we have successfully fabricated an ultra-thin and highly flexible SOFC (with a total thickness < 55μm) using simple methods including tape-casting and screen-printing. Our approach achieves the highest cell performance among reported flexible SOFCs, showcasing significant potential for advancing SOFC technologies. With the advantages of being lightweight and low in volume, our innovation opens up a wide array of applications in mobile devices, without the risk of thermomechanical fracture.
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Swatsitang, Ekaphan, Supinya Nijpanich, Sasitorn Putjuso y Thanin Putjuso. "Effect of sintering temperature and Sm3+ doping on the dielectric properties and non-Ohmic behavior of Ca1-1.5Sm Cu3Ti4.2O12 (x = 0.05 and 0.10) ceramics". Results in Physics 30 (noviembre de 2021): 104896. http://dx.doi.org/10.1016/j.rinp.2021.104896.
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Tanner, Cameron W. "(Invited) Grain Texture and Transport in Sintered Lithium Cobaltite". ECS Meeting Abstracts MA2023-02, n.º 46 (22 de diciembre de 2023): 2265. http://dx.doi.org/10.1149/ma2023-02462265mtgabs.
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Reversible exchange of lithium from lithium cobaltite (LCO) with the layered rock-salt structure was first reported by Goodenough in 1980 [1]. It has since become a critical component in the cathode of lithium-ion batteries that power portable electronics like cell phones, laptop computers, and cordless power tools. The rate of lithium diffusivity in LCO particles ranges from 10-7 to 10-11 cm²/s depending upon the state of charge and the method of measurement [2]. Lithium diffusivity in LCO because of its layered structure is also dependent upon crystallographic direction. In thin-film, micro-batteries (TFMB’s), the crystallographic orientation of LCO is controlled through choice of conditions for deposition and crystallization [3]. The diffusivity of lithium is significantly greater within rather than across the basal plane [4]. Orientations of (104) and (110) are preferred for rate performance. Continuous, roll-to-roll sintering of LCO ribbon with thicknesses down to 10 µm was recently demonstrated [5]. The LCO ribbon because it is sintered and self-supporting can in principle serve as a mechanical support to reduce the proportions of inactive battery components to dramatically increase energy density. A possible way of creating a solid-state battery with LCO ribbon is to capitalize on the LiPON solid electrolyte from TFMB’s. Both composite and dense cathodes can be envisioned. Energy densities greater than 1500 Wh/L are possible. The practicality and design of a cathode-supported battery depends upon lithium diffusion in the LCO and charge transfer resistance at the interface with the separator. Ideally, transport is sufficiently facile that acceptable rate performance in a battery is realized with cathode thickness of greater than 20 µm. In this work, we report on characterization of lithium diffusivity and ohmic losses in sintered LCO with controlled grain textures. LCO cathodes with thicknesses of 15-30 µm with random and (003) grain textures were prepared by tape casting and rapid sintering. The (hk0) texture was made by taking advantage of the (003) textured green tape; approximately 200 layers were stacked and cold-welded to form a block with a thickness of ~8 mm. The sintered block was diced to expose the edge with the favorable (hk0) orientation. Electron backscatter diffraction maps and pole figures that illustrate the grain structure and texture are shown in Fig. 1. The texture is so strong that material is orthotropic in character. Lithium diffusivity and ohmic cell resistances were determined as a function of state of charge by galvanostatic intermittent titration [7]. An average diffusivity to use as a single figure of merit was also determined by fitting of capacities measured as a function of rate of discharge from a cut-off potential of 4.3 V. Rates of lithium diffusion in sintered LCO cathodes with the (hk0) texture is 0.09 µm²/s and approximately twelve-fold greater than for the (003) texture, 0.0076 µm²/s. Ohmic loss was also found to depend upon grain texture. It was approximately 60-100 Ωcm² for (hk0) texture and >500 Ωcm² for (003). A reasonable explanation for the elevated resistance is that charge transfer occurs more easily with the (hk0) texture. [1] K. Mizushima, P.C. Jones, P.J. Wiseman, and J.B. Goodenough, Mat. Res. Bull., 15 (1980) 783-789, https://doi.org/10.1016/0025-5408(80)90012-4. [2] K. Dokko, M. Mohamedi, Y. Fujita, T. Itoh, M. Nishizawa, M. Umeda, and I. Uchida, J. Electrochem. Soc., 148 (2001) A422-A426, https://doi.org/10.1149/1.1359197. [3] J. Trask, A. Anapolsky, B. Cardozo, E. Januar, K. Kumar, M. Miller, R. Brown, and R. Bhardwaj, J. Power Sources, 350 (2017) 56-64, https://dx.doi.org/10.1016/j.jpowsour.2017.03.017. [4] J. Xie, N. Imanishi, T. Matsumura, A. Hirano, Y. Takeda, and O. Yamamoto, Solid State Ionics, 179 2008) 362-370, https://doi.org/10.1016/j.ssi.2008.02.051. [5] C. Tanner and J. Lorenzo, ECS Meet. Abstr. MA2022-02 (2022) 2482, https://doi.org/10.1149/MA2022-0272482mtgabs. [6]J.B. Bates, N.J. Dudney, G.R. Gruzalski, R.A. Zuhr, A. Choudhury, C.F. Luck, and J.D. Robertson, Solid State Ionics, 53-56 (1992) 647-654, https://doi.org/10.1016/0167-2738(92)90442-R. [7] C.J. Wen, B.A. Boukamp, R.A. Huggins, and W. Weppner, J. Electrochem. Soc., 126 (1979) 2258-2266, https://doi.org/10.1149/1.2128939. Figure 1
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Joo, Sung-Jae, JeongIn Jang, Ji-Hee Son, JongHo Park, Kim Kim y Bok-Ki Min. "A Simple Solid-State Direct Bonding Process for Fabrication of Ohmic Contacts on n-type Mg3Sb2-xBix-based Thermoelectric Materials". Korean Journal of Metals and Materials 63, n.º 1 (5 de enero de 2025): 60–67. https://doi.org/10.3365/kjmm.2025.63.1.60.
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N-type Mg3Sb2-xBix materials are expected to replace n-type bismuth telluride because they are more abundant in the Earth's crust and lower in cost. However, the metallization process of this material, which is essential to develop modules, has been relatively under-researched. According to the literature, one-step sintering process based on powder metallurgy is mostly used to form an ohmic bonding layer on n-type Mg3Sb2-xBix materials. However, this method is not reproducible nor practical, and is unsuitable for industrial mass production. This paper presents a new, simple method for metallization, the solid-state direct bonding of Mg and Cu foils on sintered n-type Mg3Sb2-xBix. It employs interdiffusion between the thermoelectric material and the metal layer at elevated temperatures to form a tight and robust bond. Mgwas chosen as the contact metal so that the interdiffusion of Mg would not cause a Mg deficiency in the Mg3Sb2-xBix near the interface. Then, a Cu layer was selected as the second metal to wrap around the Mg layer so that the subsequent soldering process could be the same as that of bismuth telluride. Solid-state bonding with the Mg/Cu double layer formed a structurally perfect joint at 723 K. When the temperature of the solid-state bonding exceeded 750 K, the eutectic point of Mg and Cu, the Mg layer was lost due to liquid phase formation. Solid-phase bonding at 723 K produced no noticeable change in the Seebeck coefficient near the interface, which would be caused by the outdiffusion of Mg from the n-Mg3Sb2-xBix. The specific contact resistance was about 53.8 μΩ cm2. This is superior to the values reported for n-type Bi2Te3-based materials. In this study, we also fabricated a Mg3Sb2-xBix (n)-Bi2Te3 (p) hybrid thermoelectric module and evaluated the output characteristics, which confirmed the high applicability of our solid-state bonding process.
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Paul, Tanmoy y Yoed Tsur. "Influence of Isovalent ‘W’ Substitutions on the Structure and Electrical Properties of La2Mo2O9 Electrolyte for Intermediate-Temperature Solid Oxide Fuel Cells". Ceramics 4, n.º 3 (16 de septiembre de 2021): 502–15. http://dx.doi.org/10.3390/ceramics4030037.
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Lanthanum molybdenum oxide (La2Mo2O9, LAMOX)-based ion conductors have been used as potential electrolytes for solid oxide fuel cells. The parent compound La2Mo2O9 undergoes a structural phase transition from monoclinic (P21) to cubic (P213) at 580 °C, with an enhancement in oxide ion conductivity. The cubic phase is of interest because it is beneficial for oxide ion conduction. In search of alternative candidates with a similar structure that might have a stable cubic phase at lower temperatures, we have studied the variations of the crystal structure and ionic conductivity for 25, 50, 62.5 and 75 mol% W substitutions at the Mo site using high-temperature X-ray diffraction, dilatometry, and impedance spectroscopy. Highly dense ceramic samples have been synthesized by solid-state reaction in a two-step sintering process. Low-angle X-ray diffraction and Rietveld refinement confirm the stabilization of the cubic phase for all compounds in the entire temperature range considered. The substitutions of W at the Mo site produce a decrement in the lattice parameter. The thermal expansion coefficients in the high-temperature range of the W-substituted ceramics, as determined by dilatometry, are much higher than that of the unmodified sample. The impedance spectra have been modeled using a modified genetic algorithm within 300–600 °C. A distribution function of the relaxation times is obtained, and the contributions of ohmic drop, grains and grain boundaries to the conductivity have been identified. Overall, our investigation provides information about cationic substitution and insights into the understanding of oxide ion conductivity in LAMOX-based compounds for developing solid oxide fuel cells.
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Pibulchinda, Pattiya y Scott A. Barnett. "(Invited) Studying Ni-YSZ Fuel Electrode Microstructure and Characteristics Using Symmetric Cells". ECS Meeting Abstracts MA2024-02, n.º 48 (22 de noviembre de 2024): 3462. https://doi.org/10.1149/ma2024-02483462mtgabs.
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Electrode-supported solid oxide cell (SOC) performance, efficiency, and stability are largely dependent on their Ni-YSZ cermet electrodes and supports. The design variables for these Ni-YSZ layers include the Ni/YSZ ratio, pore former volume fraction/size, thicknesses, and the firing conditions that partly determine their microstructures. These parameters can be used to optimize the electrode by maximizing active triple phase boundary (TPB) density in the functional layer, maximizing gas transport through the support, achieving required conductivity, maintaining mechanical strength, and minimizing overall Ni content. This study aims to investigate how Ni-YSZ characteristics affect overall electrochemical performance and mechanical strength. In the initial studies, Ni-YSZ electrode-supported symmetric cells with a single uniform Ni-YSZ layer without pore former were studied to focus on functional layer properties. Cells with different Ni contents were compared. Cells were manufactured by laminating tape-cast layers and co-sintering at high temperatures, with a YSZ electrolyte thickness of ~ 10 μm and Ni-YSZ thickness of ~ 150 μm. Initial NiO weight percentages in the NiO-YSZ slurries were varied from 45 to 70% in different cells. Although NiO-YSZ layers with different compositions are expected to have different shrinkages, we found that by sintering the symmetric cells at 1300°C, all cell configurations were free of defects, curvature, or delamination. Flexural strengths of both the electrodes and symmetric cells were characterized at ambient temperature via three-point bending tests. The NiO-YSZ composite reduction to cermet Ni-YSZ decreases flexural strength. In addition, increases in Ni content decrease flexural strength. The flexural strength results will be compared with values expected based on classic laminate plate theory. Electrochemical impedance spectroscopy measurements were taken at open circuit voltage in 97% H2-3% H2O at 650°C, 700°C, 750°C, and 800°C. The impedance results fitted well using an equivalent circuit model that includes Ohmic, transmission line, and Warburg resistance elements. The Warburg resistance, which corresponds to gas diffusion processes, decreases significantly with increasing Ni content since most of the porosity results from the reduction of NiO to Ni. In these low steam conditions, the Warburg resistance element dominates overall impedance in 45 to 65 NiO weight percent electrodes. The 50-weight percent NiO electrode was found to minimize transmission line model resistance. The correlation between impedance results and the measured electrode microstructure (e.g., porosity, tortuosity, and active TPB density) will be discussed.
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Wang, Rong-Tsu, Horng-Yi Chang y Jung-Chang Wang. "An Overview on the Novel Core-Shell Electrodes for Solid Oxide Fuel Cell (SOFC) Using Polymeric Methodology". Polymers 13, n.º 16 (18 de agosto de 2021): 2774. http://dx.doi.org/10.3390/polym13162774.
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Lowering the interface charge transfer, ohmic and diffusion impedances are the main considerations to achieve an intermediate temperature solid oxide fuel cell (ITSOFC). Those are determined by the electrode materials selection and manipulating the microstructures of electrodes. The composite electrodes are utilized by a variety of mixed and impregnation or infiltration methods to develop an efficient electrocatalytic anode and cathode. The progress of our proposed core-shell structure pre-formed during the preparation of electrode particles compared with functional layer and repeated impregnation by capillary action. The core-shell process possibly prevented the electrocatalysis decrease, hindering and even blocking the fuel gas path through the porous electrode structure due to the serious agglomeration of impregnated particles. A small amount of shell nanoparticles can form a continuous charge transport pathway and increase the electronic and ionic conductivity of the electrode. The triple-phase boundaries (TPBs) area and electrode electrocatalytic activity are then improved. The core-shell anode SLTN-LSBC and cathode BSF-LC configuration of the present report effectively improve the thermal stability by avoiding further sintering and thermomechanical stress due to the thermal expansion coefficient matching with the electrolyte. Only the half-cell consisting of 2.75 μm thickness thin electrolyte iLSBC with pseudo-core-shell anode LST could provide a peak power of 325 mW/cm2 at 700 °C, which is comparable to other reference full cells’ performance at 650 °C. Then, the core-shell electrodes preparation by simple chelating solution and cost-effective one process has a potential enhancement of full cell electrochemical performance. Additionally, it is expected to apply for double ions (H+ and O2−) conducting cells at low temperature.
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Song, Hyunghoon, Jaeseok Lee y Joongmyeon Bae. "Flatness Enhancement of Metal-Supported Solid Oxide Fuel Cells with Additional Compensation Layer". ECS Meeting Abstracts MA2023-01, n.º 54 (28 de agosto de 2023): 67. http://dx.doi.org/10.1149/ma2023-015467mtgabs.
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Solid oxide fuel cells are high-temperature fuel cells which offer several advantages: high efficiency, fuel flexibility, high-quality waste heat, and the use of non-noble metal catalysts. Metal-supported solid oxide fuel cells, in which the ceramic mechanical support layer is replaced with the metal support, are considered as next-generation solid oxide fuel cells because of their enhanced mechanical/thermal ruggedness compared to conventional ceramic-supported solid oxide fuel cells. However, different thermomechanical behavior of metal support and ceramic layers during sintering makes metal-supported cells vulnerable to warping. Cell warpage must be minimized because it reduces not only uniformity of wet-chemical coating, but also actual contact area between electrode and interconnect, increasing the contact resistance. In this study, causes of metal-supported cell warpage are identified, and the design that can minimize cell warpage is suggested for successful scale-up of metal-supported solid oxide fuel cells. Through thermomechanical and residual stress analyses, it is found that residual stress derived from coefficient of thermal expansion mismatch between electrode layers and the metal substrate is the main cause of the warpage of metal-supported solid oxide fuel cells. Based on these results, a novel design that has thicker metal protection layer on the opposite side of the electrolyte is proposed for minimizing cell warpage due to residual stress. Through the design modification, vertical deformation of 2-inch metal-supported solid oxide fuel cell can be successfully controlled to 17.36% of the previous design. Furthermore, electrochemical evaluation showed a 21% decrease in ohmic ASR and a 25% increase in peak power density after the design modification, implicating reduction of contact resistance as a result of increased contact area by enhanced flatness.
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Scheller, Maximilian, Axel Durdel, Johannes Kriegler, Alexander Frank y Andreas Jossen. "Simulation of Hybrid All-Solid-State Battery Performance Under Consideration of Ceramic-Polymer Phase Boundaries Using a Physicochemical Modelling Approach". ECS Meeting Abstracts MA2023-01, n.º 6 (28 de agosto de 2023): 992. http://dx.doi.org/10.1149/ma2023-016992mtgabs.
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With the growing interest in all-solid-state battery (ASSB) technology for high-energy and high-power applications, the electrochemical performance of cell components and production-related characteristics must be improved to achieve reliable and cost-effective scale-up of laboratory cell concepts [1]. Combining inorganic ceramic and polymer solid electrolytes (SEs) serves to tune the ionic transport and the mechanical properties of composite cathodes [2, 3]. A polymer electrolyte share in the composite cathode is expected to improve the mechanical contact between the cathode active material (CAM) and the SE, resulting in facilitated charge transfer and improved cell performance. Furthermore, polymer SEs serve to overcome the challenges of co-sintering dense composites of CAM and inorganic SE [4, 5]. In hybrid cell concepts with polymer- and inorganic ceramic SE, the ionic transport path crosses a ceramic-polymer phase boundary, which leads to additional polarization through charge transfer and ohmic resistance. State-of-the-art literature discusses the influence of ceramic particles in polymer electrolytes, but falls short on the impact of ceramic-polymer phase boundaries on the total cell performance of ASSBs [6, 7, 8]. To allow for the simulation of hybrid full cells, a pseudo-two-dimensional (p2D) physicochemical model is introduced within this work. The model is based on the Newman approach, modified with a description for the ceramic-polymer phase boundary [9]. In equilibrium state, the potential drop across the ceramic-polymer boundary was modeled with the Donnan-potential condition as recently proposed by Kim et al. [10]. Under current flow, additional polarization occurs at the interface due to electrochemical charge transfer, which was modeled by the Butler-Volmer equation, and ohmic contact resistance. The conservation of mass and charge over the phase boundary was secured with a current, flux, and a potential boundary condition. A model cell was defined (see figure 1) and parametrized using material-specific values for the ionic and electronic transport characteristics as well as the interface and charge transfer properties. Since the focus of this study was on the ceramic-polymer phase boundary, ideal plating and stripping behavior at the Li-metal anode were assumed neglecting irregular lithium deposition, e.g., lithium dendrite formation. As separator material, the well-known ceramic LLZO SE was modeled. A composite cathode with NMC-622 as CAM and PEO/LiTFSI as polymer electrolyte was assumed. The lower part of figure 1 shows the reduced 1D-model geometry and the ion transport mechanisms in each model domain. The established physicochemical model was applied to identify performance-limiting effects in hybrid ASSBs to conclude on cell designs achieving high energy and power densities. To quantify and localize the polarization contributions in each domain, arising from SE ionic conductivity, diffusion or charge-transfer processes, as well as phase boundaries, the method proposed by Nyman et al. was used [11]. Figure 2 a) shows the results of polarization analysis when simulating a 0.1C charge, while figure 2 b) depicts the results for a 1C charge. Diffusion limitation in the polymer electrolyte led to high concentration gradients in the polymer-phase of the composite cathode, resulting in high diffusion polarization at elevated charging rates as shown in figure 2 b). This determined a critical current density at cell level, which was caused by large Li-ion concentration gradients and a possible depletion of Li-ions near the ceramic separator. The overall cell polarization was further enhanced by the ceramic-polymer phase boundary. For the contact case of LLZO versus PEO/LiTFSI considered here, the equilibrium potential between the phases was calculated according to the theory of Donnan to 31 mV. Since a wide range of values for the contact resistance at the ceramic-polymer interface is reported in the literature [6, 7], ohmic polarization could be important and was therefore evaluated as a function of different contact resistances. A critical contact resistance was determined to achieve the requirements for future battery technologies regarding energy and power density. Figure 1
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Ozaki, Ryota, Yohei Nagatomo, Ko Yoshiga, Tsutomu Kawabata, Mio Sakamoto, Masahiro Yasutake, Yuya Tachikawa, Junko Matsuda y Kazunari Sasaki. "Electrochemical Performance of Fuel-Electrode-Supported Reversible Solid Oxide Cells with a Ni-GDC Functional Layer". ECS Meeting Abstracts MA2024-02, n.º 48 (22 de noviembre de 2024): 3452. https://doi.org/10.1149/ma2024-02483452mtgabs.
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Introduction Reversible solid oxide cells (r-SOCs) can generate electricity in SOFC mode and produce hydrogen in SOEC mode. R-SOCs are promising electrochemical energy devices that can manage power derived from renewable energy sources by switching operating modes (1). Fuel-electrode-supported cells, which are widely used in both SOFCs and SOECs, exhibit higher performance even at lower operation temperature due to the use of thin electrolytes. Ni-yttria-stabilized zirconia (YSZ) is widely used as the fuel electrode material in fuel-electrode-supported cells because of its high ionic conductivity, high catalytic activity, and compatibility with electrolyte materials. However, Ni-zirconia based cermet such as Ni-YSZ tends to exhibit high polarization resistance, especially in the SOEC mode (2). Furthermore, degradation in the SOEC mode is also an issue (3), and further improvement of electrochemical performance and durability is necessary for the practical use of r-SOCs. Gadolinia-doped ceria (GDC) has higher ionic conductivity than YSZ, and, as a mixed ionic electronic conductor, the electrochemical reaction extends not only to the triple phase boundary (TPB) but also to the double phase boundary (DPB). Therefore, the electrochemical performance is expected to be improved by substituting Ni-YSZ with Ni-GDC. Here, in this study, a fuel-electrode-supported reversible solid oxide cell is prepared with a Ni-YSZ fuel electrode support and a thin Ni-GDC fuel electrode functional layer next to the electrolyte, and the electrochemical performance is evaluated. Experimental For experiments, a fuel-electrode-supported reversible solid oxide cell was used, as schematically described in Fig. 1. The cell consisted of a fuel electrode support, a fuel electrode functional layer, an electrolyte, a GDC buffer layer, and an air electrode. The materials of the fuel electrode support, the fuel electrode functional layer, and the electrolyte were Ni-(Y2O3)0.08(ZrO2)0.92 (YSZ), Ni-Gd0.1Ce0.9O2 (GDC), and YSZ, respectively, and the half-cell was fabricated by co-sintering these three layers. GDC has been reported to form a highly resistive solid solution with YSZ at high temperatures (4). Therefore, half-cells were fabricated at different co-sintering temperatures to investigate the influence of such solid solution on the cell performance. La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) was used for the air electrode, and the GDC buffer layer was inserted between the electrolyte and the air electrode to suppress interdiffusion. Current-voltage (I-V) characteristics were measured at 700–800 °C with a supply of 100 ml min-1 of 50%-humidified hydrogen (50 %H2O-50 %H2) to the fuel electrode, and 150 ml min-1 of air to the air electrode. Electrochemical impedance spectra were measured in the frequency range from 1 MHz to 0.1 Hz. Results and discussion Figure 2 (a) shows the I-V characteristics at 800 °C of the cells co-sintered at 1300 °C and 1350 °C. The cell co-sintered at 1300 °C exhibited higher I-V characteristics than the cell co-sintered at 1350 °C in both SOFC and SOEC modes. In the SOEC mode, the electrolysis current densities at the thermo-neutral potential (~1.29 V) of the cells co-sintered at 1350 °C and 1300 °C were 1.05 A cm-2 and 1.15 A cm-2 under these fabrication conditions, respectively. Both ohmic and polarization resistances were lower in the cells co-sintered at 1300 °C than in the cells co-sintered at 1350 °C, suggesting that lowering co-sintering temperatures than 1300 °C may further improve their I-V characteristics. The improvement in electrochemical performance by lowering the co-sintering temperature from 1350 °C to 1300 °C can be attributed to several factors, including an increase in TPB density due to a finer fuel electrode microstructure and a suppression of YSZ-GDC solid solution formation. A detailed analysis of these factors is needed in the future. In this presentation, the electrochemical performance of cells co-sintered at lower temperatures more than 1300 °C and the comparison of the performance of Ni-GDC functional layers with that of Ni-YSZ functional layers will also be presented and discussed. References Q. Minh, and M. B. Mogensen, Electrochem. Soc. Interface, 22, 55 (2013). Endo, T. Fukumoto, Y. Tachikawa, S. M. Lyth, J. Matsuda, and K. Sasaki, ECS Trans., 109 (11), 3 (2022). Moçoteguy, and A. Brisse, Int. J. Hydrogen Energy, 38, 15887 (2013). Tsoga, A. Naoumidis, and D. Stöver, Solid State Ionics, 135, 403 (2000). Figure 1
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Asghar, Muhammad Imran y Peter D. Lund. "Hybrid Manufacturing of a Single-Layer Ceramic Fuel Cell Utilizing 3D Printing and Laser Scribing". ECS Meeting Abstracts MA2022-01, n.º 38 (7 de julio de 2022): 1677. http://dx.doi.org/10.1149/ma2022-01381677mtgabs.
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Single-layer ceramic fuel cells are developing as a promising fuel cell technology [1-3]. Since 3D printing can create both the dense and the porous structures with good mechanical and electrochemical properties, it has the potential to revolutionize the manufacturing of fuel cells. We recently reported a 3D printed single-layer ceramic fuel cell fabricated through an extrusion-based 3D printing, which generated a power density of 230 mW/cm2 at 550oC [1]. A comprehensive investigation into the influence of sintering temperatures ranging from 700oC to 1000oC assisted us in optimizing the density of the functional layer for acceptable electrochemical performance while maintaining adequate mechanical properties. We noticed that the performance of the single-layer cells was limited by the mass transport losses due to low porosity of the single-layer. The best printed cell suffered from a high ohmic loss (0.46 Ω.cm2) and a polarization loss (0.32 Ω.cm2) [1]. In this work, we used a hybrid of a 3D printer and a laser scriber to fabricate the patterned single-layer ceramic fuel cells. Interestingly, the performance of the patterned single-layer ceramic fuel cell was 30% better as compared to a conventional single-layer fuel cell without any patterns. The patterned structures on the surfaces of the cell obtained through the laser scribing, considerably improved the electrode processes. In the patterned 3D printed fuel cells, we studied several electrode materials such as CuFe2O4, LSCF, LSC, NiCoAlLi-oxide, and LiNiZn-oxide and synthesized pastes appropriate for extrusion-based 3D printing. The rheological characteristics of the pastes were investigated using several characterization techniques such as dynamic light scattering, viscometry and tensiometry. Electrochemical impedance spectroscopy and current-voltage measurements were used to assess the electrochemical performance of the cells. Furthermore, high-temperature XRD demonstrated the composite materials' excellent structural stability. To further understand the processes in the cells, additional spectroscopic and microscopic investigations (HR-TEM, SEM-EDX, XPS) were performed. Acknowledgement. Dr. Asghar thanks Academy of Finland (Grant No. 13322738, 13329016) and the Hubei overseas Talent 100 program for their support. References [1] M. I. Asghar, P. Mäkinen, S. Virtanen, A. Maitre, M. Borghei and P. D. Lund, P.D., Nanomaterials 11 (2021) 2180. [2] M. I. Asghar, X. Yao, S. Jouttijärvi, E. Hochreiner, R. Virta and P. D. Lund, Materials International Journal of Hydrogen energy, 45 (2020) 24083. [3] M. I. Asghar, S. Jouttijärvi, R. Jokiranta, A. Valtavirta and P. D. Lund, Nanoenergy, 53 (2018) 391. Figure 1
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Kuroha, Tomohiro, Kosuke Yamauchi, Yuichi Mikami y Yuji Okuyama. "Development of Protonic Ceramic Fuel Cell Using BaZr0.2Yb0.8O3-δ as the Electrolyte". ECS Meeting Abstracts MA2023-01, n.º 54 (28 de agosto de 2023): 225. http://dx.doi.org/10.1149/ma2023-0154225mtgabs.
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Protonic Ceramic Fuel Cells (PCFCs) are attracting attention as next-generation fuel cells that are expected to have lower operating temperatures and higher power generation efficiency than SOFCs. We have reported that BaZr0.8Yb0.2O3-δ does not chemically react with NiO used as a fuel electrode at 1475°C, which is the sintering temperature of the cell, and that the fuel cell can be fabricated by the tape casting method and the fuel electrode and electrolyte co-firing method used in industrial production processes for SOFCs and electronic components. This report describes issues that need to be resolved for the practical application of this cell. Fuel cells were fabricated by laminating green sheets prepared by the tape casting method and co-firing the electrolyte and fuel electrode together. For the air electrode, La0.6Sr0.4Co0.2Fe0.8O3-δ and La0.6Sr0.4CoO3-δ, which are widely used in SOFCs, and newly developed BaZr0.375Yb0.125Co0.5O3-δ were sintered at 900°C to 1000°C. The electrochemical performance of the planar cell was investigated at 600°C under the conditions of a humid fuel gas (i.e., 3% H2O and 97% H2) and humid air (i.e., 3% H2O, 20% O2 and 77% N2). The active area of the planar cell was 0.785 cm2. To evaluate the durability of each cell, continuous power generation tests were conducted at constant current. The durability test was conducted by generating power for 1000 hours at a constant current that resulted in a voltage of 0.85 V at the start of the test, and durability was evaluated by the rate of voltage drop per 1000 hours. As a result, the voltage reduction rate per 1000 hours for the cell using BaZr0.375Yb0.125Co0.5O3-δ as the air electrode was 7.3%/kh. The results clearly show that one of the most significant issues for practical use is the suppression of the rate of voltage drop. The resistance of the cell before and after the durability test were analyzed by electrochemical impedance method, and the ohmic resistance and electrode resistance increased. EPMA analysis of the cell cross section to investigate the cause of degradation revealed diffusion of Ni from the fuel electrode and Co from the air electrode in the electrolyte. Therefore, in order to further improve durability, there is a need to consider adding an anti-diffusion layer to prevent the diffusion of these elements and developing air electrode materials that do not contain Co.
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Ioannidou, Evangelia, Stylianos G. Neophytides y Dimitris K. Niakolas. "(Digital Presentation) Au-Mo-Fe-Ni/CeO2(Gd2O3) As Potential Fuel Electrodes for Internal CO2 Reforming of CH4 in Single SOFCs". ECS Meeting Abstracts MA2023-01, n.º 54 (28 de agosto de 2023): 378. http://dx.doi.org/10.1149/ma2023-0154378mtgabs.
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Recycling biogas to produce syngas (H2 + CO) through Dry Reforming of Methane (DRM) has currently attract resurgent interest. Biogas consists mainly of CH4 (55-65%) and CO2 (35-45%) and is widely produced by anaerobic fermentation of biomass [1]. DRM provides a feasible solution to eliminate greenhouse gases via production of useful chemicals and hydrocarbons. Considering the DRM energy applications the produced syngas can be used as a fuel in high temperature solid oxide fuel cells (SOFCs) for electricity production or biogas can be directly fueled in the cell without the need of an external reformer (Internal Dry Reforming of Methane, IDRM), which simplifies the SOFC system and reduces the cost [2,3]. Specifically, during IDRM at temperatures higher than 800 oC, the catalytic Reverse Water Gas Shift (RWGS) reaction may run in parallel with electrocatalytic reactions, resulting in the consumption of valuable H2. In addition, carbon deposition on the electrocatalyst surface due to CH4 decomposition, which is favored at elevated temperatures (≥ 700 oC), may also occur resulting in progressive electrocatalyst deactivation [4]. Ni-based ceramic-metal composites with Yttria Stabilized Zirconia (YSZ) and Gadolinia Doped Ceria (GDC) are widely used as electrocatalysts in SOFCs because of their activity and inexpensiveness. However, nickel catalyses the formation of carbon deposits from hydrocarbons and exhibits a tendency to agglomerate after prolonged operation [3,4]. The carbon tolerance and anti-sintering tendency of nickel and specifically of Ni/GDC can be enhanced, by dispersing trace amounts of transition noble (Rh, Pt, Pd, Ru, Au) or non-noble (Co, Cu, Mo, Fe) metal elements [3,5]. In this study the catalytic and electro-catalytic performance, as well as the coking resistance of Au (1 and 3 wt.%), Mo (0.4 wt.%) and Fe (0.5 and 2 wt.%) modified Ni/CeO2(Gd2O3) electro-catalysts were studied as half and full electrolyte supported cells under internal CO2 reforming of CH4 in single SOFCs, at 750-900 oC. The aim was to elucidate their activity towards the consumption of CH4, CO2, the production of H2, H2O, CO and the production of carbon, as a function of temperature and the applied current density under a biogas fuel mixture of CH4/CO2=1. Additionally, the cells comprising a modified Ni/GDC fuel electrode, an 8 mol% Y2O3 stabilized ZrO2 (8YSZ) electrolyte were characterized using I-V measurements and Electrochemical Impedance Spectra (EIS) analysis in order to investigate the evolution of the ohmic and polarization resistance values as a reflection of current. Complementary physicochemical characterization includes thermo-gravimetric measurements for the catalytic dissociation of CH4 and CO2 at 800 oC. In brief, the cell with Ni/GDC was more active catalytically compared to the modified cells, but exhibited worst electrocatalytic performance. The cells with 3 wt.% Au-0.4 wt.% Mo-Ni/GDC and 3 wt.% Au-0.5 wt.% Fe-Ni/GDC fuel electrodes were moderately active catalytically, but performed better. The main degradation factor for the unmodified cell was the higher carbon formation, which increased gradually with the increased current and was reflected on higher ohmic and polarization resistance values compared to the modified cells. Acknowledgments This research has been co-financed by the European Union and Greek national funds through the operational program ‘Regional Excellence’ and the operational program ‘Competitiveness, Entrepreneurship and Innovation’, under the call “RESEARCH-CREATE-INNOVATE” (Project code: T2EΔK-00955). References [1] Escudero, M.J., Maffiotte, C.A. & Serrano, J.L. (2021). J. Power Sources. 481 (20) 229048. [2] Souentie, S., Athanasiou, M., Niakolas, D.K., Katsaounis, A., Neophytides, S.G. & Vayenas, C.G. (2013). J. Catal. 306: 116-128. [3] Neofytidis, Ch., Dracopoulos, V., Neophytides, S.G. & Niakolas, D.K. (2018). Catal. Tod. 310: 157-165. [4] Pakhare, D. & Spivey, J. (2014). Chem. Soc. Rev. 43: 7813-7837. [5] Niakolas, D.K., Neofytidis, Ch., Neophytides, S.G. (2017). Frontiers in Environ. Science. 5: 78.
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Slomski, Heather S., Jonas Kaufman, Michael Dzara, Nicholas A. Strange, Jeremy Hartvigsen, Nicholas Kane, Micah Casteel et al. "(Invited) Early-Onset Degradation of (La,Sr)(Co,Fe)O3 in Solid Oxide Electrolysis Cells". ECS Meeting Abstracts MA2024-02, n.º 48 (22 de noviembre de 2024): 3347. https://doi.org/10.1149/ma2024-02483347mtgabs.
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The increasing need for global hydrogen ideally depends on low-cost 1$/kg green hydrogen. The DOE’s Energy Earthshot initiative aims to reduce the cost of green hydrogen to achieve this goal in a decade. There are a number of pathways of which solid oxide electrolysis cells (SOECs) are one of the most attractive1. SOECs have high demonstrated efficiency for hydrogen production without precious metal catalysts but at present with limited lifetimes2–4. SOEC’s have a layered structure consisting of an LSCF-GDC composite cathode (La0.6Sr0.4Co0.2Fe0.8O3-δ / gadolinium doped ceria), a GDC barrier layer, YSZ (yttrium stabilized zirconia) electrolyte, and Ni-YSZ anode support layer. This structure exhibits various degradation mechanisms initiating at both the air and fuel electrode at high operating temperatures predominately at the interfaces5,6. Understanding the mechanisms behind cell degradation and their potential effects on cell performance is critical to reach hydrogen Earthshot goals. There has been significant focus on the coarsening of Ni in the fuel electrode and advancement made in reducing its negative effects on cell performance over time 7. Another significant mechanism is due to the degradation of LSCF at temperatures above 550 °C 8. As LSCF degrades, Sr migrates from the structure and becomes mobile throughout the cell. This poses problems as it reaches the electrolyte and forms SrZrO3 which causes both ohmic losses and potential mechanical failure9. This study focuses on the initiation of this mechanism and its progression in the break in period of the cell. Extensive characterization of early-onset degradation is achieved through SEM (Scanning Electron Microscopy), STEM EDS (Scanning Transmission Electron Microscopy), XANES (X-ray Absorption Near Edge Structure) and Synchrotron XRD (X-ray Diffraction). These techniques are then paired with first principles calculations of the 6428-LSCF phase stability in modeling the stoichiometric changes to rhombohedral LSCF in the cell. Together this allows us to achieve spatial mapping, phase progression over time, and predict stoichiometry changes in early onset degradation. These methods identify several unique phases that result from the degradation of LSCF some of which are known to impact cell lifetimes. Identifying the pathways of early onset degradation allows for mitigation strategies to be developed for cell sintering and fabrication. (1) Hydrogen Shot. Energy.gov. https://www.energy.gov/eere/fuelcells/hydrogen-shot (accessed 2024-04-18). (2) Laguna-Bercero, M. A. Recent Advances in High Temperature Electrolysis Using Solid Oxide Fuel Cells: A Review. J. Power Sources 2012, 203, 4–16. https://doi.org/10.1016/j.jpowsour.2011.12.019. (3) Elder, R.; Cumming, D.; Mogensen, M. B. Chapter 11 - High Temperature Electrolysis. In Carbon Dioxide Utilisation; Styring, P., Quadrelli, E. A., Armstrong, K., Eds.; Elsevier: Amsterdam, 2015; pp 183–209. https://doi.org/10.1016/B978-0-444-62746-9.00011-6. (4) Ferrero, D.; Lanzini, A.; Santarelli, M.; Leone, P. A Comparative Assessment on Hydrogen Production from Low- and High-Temperature Electrolysis. Int. J. Hydrog. Energy 2013, 38 (9), 3523–3536. https://doi.org/10.1016/j.ijhydene.2013.01.065. (5) Hauch, A.; Jensen, S. H.; Ramousse, S.; Mogensen, M. Performance and Durability of Solid Oxide Electrolysis Cells. J. Electrochem. Soc. 2006, 153 (9), A1741. https://doi.org/10.1149/1.2216562. (6) Kanae, S.; Toyofuku, Y.; Kawabata, T.; Inoue, Y.; Daio, T.; Matsuda, J.; Chou, J.-T.; Shiratori, Y.; Taniguchi, S.; Sasaki, K. Microstructural Characterization of SrZrO3 Formation and the Influence to SOFC Performance. ECS Trans. 2015, 68 (1), 2463. https://doi.org/10.1149/06801.2463ecst. (7) Mogensen, M. B.; Chen, M.; Frandsen, H. L.; Graves, C.; Hauch, A.; Hendriksen, P. V.; Jacobsen, T.; Jensen, S. H.; Skafte, T. L.; Sun, X. Ni Migration in Solid Oxide Cell Electrodes: Review and Revised Hypothesis. Fuel Cells 2021, 21 (5), 415–429. https://doi.org/10.1002/fuce.202100072. (8) Tai, L.-W.; Nasrallah, M. M.; Anderson, H. U.; Sparlin, D. M.; Sehlin, S. R. Structure and Electrical Properties of La1 − xSrxCo1 − yFeyO3. Part 2. The System La1 − xSrxCo0.2Fe0.8O3. Solid State Ion. 1995, 76 (3), 273–283. https://doi.org/10.1016/0167-2738(94)00245-N. (9) Lu, Z.; Darvish, S.; Hardy, J.; Templeton, J.; Stevenson, J.; Zhong, Y. SrZrO3 Formation at the Interlayer/Electrolyte Interface during (La1-xSrx)1-δCo1-yFeyO3 Cathode Sintering. J. Electrochem. Soc. 2017, 164 (10), F3097. https://doi.org/10.1149/2.0141710jes.
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Uchida, Hiroyuki, Eman H. Da'as, Hanako Nishino, Rajakumaran Ramachandran, Yosuke Takahashi y Yuuki Yamada. "Performances of Ni−SDC Hydrogen Electrodes in Reversible Operation Between SOEC and SOFC-Modes". ECS Meeting Abstracts MA2023-01, n.º 54 (28 de agosto de 2023): 115. http://dx.doi.org/10.1149/ma2023-0154115mtgabs.
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A reversible solid oxide cell (R-SOC), which can be operated as solid oxide electrolysis cell (SOEC) and solid oxide fuel cell (SOFC), is a highly efficient direct energy converter between hydrogen and electricity (1). We have engaged in the R&D of high-performance, durable electrodes for the R-SOC (2-13). Recently, it was found that the durability of a double-layer H2 (DL) electrode, consisting of a SDC scaffold [samaria-doped ceria (CeO2)0.8(SmO1.5)0.2] with highly dispersed Ni0.9Co0.1 nanoparticles as the catalyst layer and a thin current collecting layer of Ni–YSZ cermet, was improved greatly by a reversible cycling operation between the SOEC and SOFC modes (12). The microstructure was observed to be stabilized by the cycling operation, i.e., lower parts of many Ni‒Co particles were anchored tightly on the SDC support and some portions were coated with SDC film, with certainty due to a strong interaction between Ni‒Co and SDC (13). However, the procedure for dispersing Ni‒Co nanoparticles on SDC (via an impregnation method) is not always suitable for large-scale fabrication. Aiming to develop a durable, practical hydrogen electrode with such a stabilized microstructure, we prepared new Ni–SDC hydrogen electrodes by a convenient protocol and examined the performances in the reversible operation. We prepared a coin-size cell with an air reference electrode (ARE) (6, 9-12): Ni–SDC H2 electrode│YSZ (0.5 mm)│SDC interlayer│LSCF–SDC O2 electrode For the H2 electrode, a paste was prepared by mixing Ni nanoparticles with uniform size (prepared by Noritake Co., Limited), SDC powder, and pore former. The paste was painted on YSZ electrolyte, followed by sintering. The LSCF–SDC (40 vol.% SDC) oxygen electrode was prepared on the SDC interlayer in the same manner as that described in our work (7). Test cells were operated at 800ºC by supplying humidified H2 (p[H2O] = 0.4 atm) to the H2 electrode compartment and dry O2 to the O2 electrode, irrespective of operation modes (SOEC or SOFC). The steady-state IR-free polarization curves (I–E curves) of the electrodes with area-specific ohmic resistances were measured by the current-interruption method in a three-electrode configuration. Figure 1 shows a SEM image acquired with a back-scattered electron (BSE) detector and Ni mapping by an energy-dispersive X-ray spectrometer (EDX) for the cross section of Ni–SDC electrode in pristine condition. In the BSE image, SDC is observed as light gray, Ni as dark gray, and pores as black. The distribution of Ni particles are fairly uniform in the electrode. The Ni–SDC electrode thus prepared exhibited a comparable initial performance to that of our DL-H2 electrode with Ni‒Co dispersed SDC prepared by the impregnation method (12). The durability tests of the electrodes are under progress in reversible cycling between −0.50 A cm−2 (SOEC-mode for 11 h) and 0.50 A cm−2 (SOFC-mode for 11 h). This work was supported by funds for the “Collaborative Industry-Academia-Government R&D Project for Solving Common Challenges toward Dramatically Expanded Use of Fuel Cells” from the New Energy and Industrial Technology Development Organization (NEDO) of Japan. References S. D. Ebbesen, S. H. Jensen, A. Hauch, and M. B. Mogensen, Chem. Rev., 114, 10697 (2014). H. Uchida, N. Osada, and M. Watanabe, Electrochem. Solid-State Lett., 7, A500 (2004). N. Osada, H. Uchida, and M. Watanabe, J. Electrochem. Soc., 153, A816 (2006). Y. Tao, H. Nishino, S. Ashidate, H. Kokubo, M. Watanabe, and H. Uchida, Electrochim. Acta, 54, 3309 (2009). R. Nishida, P. Puengjinda, H. Nishino, K. Kakinuma, M. E. Brito, M. Watanabe, and H. Uchida, RSC Adv., 4, 16260 (2014). H. Uchida, P. Puengjinda, K. Miyano, K. Shimura, H. Nishino, K. Kakinuma, M. E. Brito, and M. Watanabe, ECS Trans., 68 (1), 3307 (2015). K. Shimura, H. Nishino, K. Kakinuma, M. E. Brito, and H. Uchida, Electrochim. Acta, 225, 114 (2017). K. Shimura, H. Nishino, K. Kakinuma, M. E. Brito, and H. Uchida, J. Ceram. Soc. Jon., 125, 218 (2017). P. Puengjinda, H. Nishino, K. Kakinuma, M. E. Brito, and H. Uchida, J. Electrochem. Soc., 164, F889 (2017). H. Uchida, P. Puengjinda, K. Shimura, H. Nishino, K. Kakinuma, and M. E. Brito, ECS Trans., 78 (1), 3189 (2017). H. Uchida, H. Nishino, K. Kakinuma, and M. E. Brito, ECS Trans., 91 (1), 2379 (2019). H. Uchida, H. Nishino, P. Puengjinda, and K. Kakinuma, J. Electrochem. Soc., 167, 134516 (2020). H. Uchida, H. Nishino, and E. Da’as, ECS Trans., 103 (1), 6119 (2021). Figure 1
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Afonin, Nikolay N. y Vera A. Logachova. "Reactive Interdiffusion of Components in a Non-Stoichiometric Two‑Layer System of Polycrystalline Titanium and Cobalt Oxides". Kondensirovannye sredy i mezhfaznye granitsy = Condensed Matter and Interphases 22, n.º 4 (26 de noviembre de 2020): 430–37. http://dx.doi.org/10.17308/kcmf.2020.22/3058.
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We demonstrated the possibility of using the mathematical form of Darken's theory, applied to the description of the Kirkendall effect in binary systems, to the description of reactive interdiffusion in non-stoichiometric polycrystalline film oxide systems with limited solubility. The aim of the study was the simulation of reactive interdiffusion under vacuum annealing of a thin film system consisting of two non-stoichiometric polycrystalline titanium and cobalt oxides. The nonstoichiometric nature of the system assumes the presence of mobile components, free interstitial cobalt and titanium cations in it. Phase formation occurs as a result of reactive interdiffusion and trapping of mobile components of the systemon inter-grain traps. The proposed mechanism describes the formation of complex oxide phases distributed over the depth of the system.A complex empirical research technique was used, involving Rutherford backscattering spectrometry, X-ray phase analysis and modelling methods. The values of the characteristic parameters of the process were determined by numerical analysis of the experimentally obtained distributions of the concentrations of the components within the developed model. During vacuum annealing of a thin film two-layer system of non-stoichiometric TiO2–x–Co1–уO oxides in temperature range T = 773 – 1073 К, the values of the individual diffusion coefficients of cobalt DCo = 5.1·10–8·exp(–1.0 eV/(kT) cm2/s and titaniumDTi = 1.38·10–13·exp(–0.31 eV/(kT) cm2/s were determined.It was shown that for T = 1073 K, the phase formation of CoTiO3 with a rhombohedral structure occurs. The extension of the phase formation region of complex cobalt and titanium oxides increases with an increase in the vacuum annealing temperature and at 1073 K it is comparable with the total thickness of the film system.The model allows predicting the distribution of the concentrations of the components over the depth of multilayer nonstoichiometric systems in which reactive interdiffusion is possible.
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Cibuzar, Gregory T. "Sintered Ohmic Contacts to GaAs". MRS Proceedings 240 (1991). http://dx.doi.org/10.1557/proc-240-443.
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ABSTRACTThe formation of reliable low resistance ohmic contacts to GaAs and other III-IV compound semiconductors is essential for useful device and circuit fabrication. We have modified the standard AuGe ohmic contact process by using rapid thermal annealing at temperatures less than the AuGe eutectic temperature to form contacts based on sintering rather than alloying. Compared with alloyed contacts, sintered contacts have similar electrical performance, superior morphology, and improved reliability. Results from secondary mass spectroscopy analysis of sintered and alloyed contacts will be discussed.
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Schmitz, K. M., K. L. Jiao, R. Sharama, W. A. Anderson, G. Rajeswaran, L. R. Zheng, M. W. Cole y R. T. Lareau. "Pd/Au:Be Ohmic Contacts to p-Type GaAs". MRS Proceedings 163 (1989). http://dx.doi.org/10.1557/proc-163-993.
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AbstractStable, low resistance ohmic contacts to p-type GaAs were studied for use in semiconductor laser applications. Comparison was made between Cr/Au, Au:Be and Pd/Au:Be metallizations. Regions of P+ were formed in N-type GaAs by a spin-on source which was rapid diffused at 950°C for 6s. Surface doping of 2×1020/cm3 and junction depth of 0.4 μm were determined by SIMS, groove and stain, and electrochemical profile. Metallizations were accomplished by thermal evaporation with a base pressure of 3×10-6 Torr. Sintering of the metallizations was done by furnace or RTA at 350°C. This sintering temperature was selected after RBS studies predicted an absence of significant interdiffusion. Pd/Au:Be yielded the best result of 0.3 μΩ-cm2 based upon transmission line, cross-bridge Kelvin and van der Pauw studies. A layer of BeO was revealed on the surface of Au:Be contacts by Auger studies. Cross-section TEM studies on Pd/Au:Be revealed a uniform layer of alloyed Ga-Au with an absence of spiking.
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DeVoe, Emily y Silvana Andreescu. "Review—Catalytic Electrochemical Biosensors for Dopamine: Design, Performance, and Healthcare Applications". ECS Sensors Plus, 1 de abril de 2024. http://dx.doi.org/10.1149/2754-2726/ad3950.
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Abstract The effect of an Al2TiO5 (ALT) interlayer between Ni and YSZ on enhancing the thermal stability of Ni-YSZ solid oxide fuel cell was examined. Atomic layer deposition (ALD) was used to provide precise control of the structure and thickness of the ALT interlayer. The study’s findings demonstrate that a 2 nm thick ALT interlayer deposited by ALD does not adversely affect the cell’s ohmic resistance and effectively prevents Ni sintering and the loss of active area during high-temperature heat treatments. ALT layers thicker than 2 nm, although they enhanced Ni stability, were found to impede oxygen ion transport in the electrode and significantly increase the ohmic resistance of the cell, leading to a decline in performance.
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Feng, Zhuoming, Katherine Elizabeth Hansen, Harish Bhandari y John Vohs. "Stabilization of Ni-YSZ Anodes in Solid Oxide Fuel Cells using an ALD-Grown Aluminum Titanate Interlayer". ECS Advances, 28 de marzo de 2024. http://dx.doi.org/10.1149/2754-2734/ad38cd.
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Abstract The effect of an Al2TiO5 (ALT) interlayer between Ni and YSZ on enhancing the thermal stability of Ni-YSZ solid oxide fuel cell was examined. Atomic layer deposition (ALD) was used to provide precise control of the structure and thickness of the ALT interlayer. The study’s findings demonstrate that a 2 nm thick ALT interlayer deposited by ALD does not adversely affect the cell’s ohmic resistance and effectively prevents Ni sintering and the loss of active area during high-temperature heat treatments. ALT layers thicker than 2 nm, although they enhanced Ni stability, were found to impede oxygen ion transport in the electrode and significantly increase the ohmic resistance of the cell, leading to a decline in performance.