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Peng, Zhiming, Xuejun Jin, T. Y. Hsu (Xu Zuyao) et Emmanouel Pagounis. « Relaxation of twin boundaries in a Ni2MnGa single crystalline ». Materials Science and Engineering : A 481-482 (mai 2008) : 310–13. http://dx.doi.org/10.1016/j.msea.2006.11.180.
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Tachibana, Tomihisa, Takashi Sameshima, Takuto Kojima, Koji Arafune, Koichi Kakimoto, Yoshiji Miyamura, Hirofumi Harada, Takashi Sekiguchi, Yoshio Ohshita et Atsushi Ogura. « Evaluation of Silicon Substrates Fabricated by Seeding Cast Technique ». Materials Science Forum 725 (juillet 2012) : 133–36. http://dx.doi.org/10.4028/www.scientific.net/msf.725.133.
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We evaluated the properties of crystalline defects in silicon substrate, and clarified the origin of small-angle grain boundaries. In order to eliminate the effects of grain boundaries, the ingot was fabricated by unidirectional solidification technique with seed crystal. In single-crystalline region, Σ3 twin boundaries and SiC precipitates were observed near the seed crystal. No obvious relationship between twin boundaries and precipitates was observed. These defect decreased once and the precipitations appeared again. The density of precipitates increased through the crystal growth procedure. These precipitates were consisted of Si, C, and N. After the precipitation density increased, the small-angle grain boundaries appeared and some precipitates were observed at the boundaries. We considered the precipitations consisted of light element impurities such as C and N were one of the major origins of the small-angle grain boundary generation.
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Carter, C. Barry, et Lisa A. Tietz. « Interfaces in high-Tc superconducting oxides ». Proceedings, annual meeting, Electron Microscopy Society of America 47 (6 août 1989) : 178–79. http://dx.doi.org/10.1017/s0424820100152860.
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Interfaces in high-Tc superconducting oxides are influential during both the processing of bulk materials and the growth of thin epitactically aligned layers. In the first case, the formation of the superconducting phase involves the movement of phase boundaries during the solid-state reaction, while in the second, the phase boundary is formed as the superconducting material grows on the single-crystal substrate. Having formed the superconducting material, the superconducting phase will, in general, contain a large number of grain boundaries varying from the simple twin boundaries which can be produced during the cubic-to-tetragonal transformation, to low-angle grain boundaries, special high-angle grain boundaries, other high-angle grain boundaries and phase boundaries due to incomplete or on-going solid-state reactions. During the course of this presentation, recent results on these topics will be reviewed, paying particular attention to the more widely studied material, YBa2Cu3O6+x.The importance of grain boundaries in high-Tc superconducting oxides has been firmly established by the systematic analysis of Dimos et al who have shown that the misorientation of the grains in layers of YBa2Cu3O6+x which had been grown on polycrystalline SrTiO3 substrate varies with the relative misorientation between the grains.
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Rothová, Vĕra. « Diffusion in the Presence of Twin Boundaries ». Defect and Diffusion Forum 263 (mars 2007) : 201–6. http://dx.doi.org/10.4028/www.scientific.net/ddf.263.201.
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In this paper, four examples from the literature are introduced in which the presence of high density of twin boundaries could explain an anomalous diffusion behavior. (i) In the case of the grain boundary (GB) self-diffusion in nickel, leakage from the random GBs to considerably high fraction of deformation and/or annealing twins in the samples studied can be a reason for the diverse literature values of activation enthalpy. The diffusion model including participation of two types of GBs is essential for data evaluation. (ii) Segregation of Ge atoms with negligible solubility to twin boundaries and diffusion in both type A and type AB transition regime can clarify the unusual 71Ge diffusion in the Mg alloys. (iii) Anomalous diffusion of gold in polycrystalline silicon presented in the literature was discussed here. Because profiles corresponding to type AB transition regime were detected, transition from type B to type A diffusion regime could be an alternative explanation of the anomaly. (iv) Effective diffusion of the 63Ni tracer in the presence of unidirectional defects in single-crystalline β-tin might be a simple reason for the uncommon features published earlier: low activation enthalpy, high diffusion anisotropy and values of the extrapolated solid-state Ni diffusion coefficients above those in the Sn liquid phase.
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Simpson, Yonn Kouh, et C. Barry Carter. « The interaction between basal-twin boundaries and a glassy phase in α-Alumina compacts ». Proceedings, annual meeting, Electron Microscopy Society of America 46 (1988) : 570–71. http://dx.doi.org/10.1017/s0424820100104911.
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Understanding the nature of glass/crystalline interfaces is not only of fundamental scientific interest but is directly relevant to the liquid-phase sintering of polycrystalline ceramics such as α-alumina. Faceting behavior of alumina in the presence of SiO2 glass has been of much interest in the field of sintering with respect to the grain growth and the grain boundary mobility during sintering. The study of grain boundaries containing a glassy phase in alumina compacts is difficult however, since many of the TEM techniques presently available for the identification of a glassy phase at grain boundaries can give ambiguous results due to grain boundary grooving. A method for systematically studying glassy / crystalline interfaces without such ambiguity is therefore needed. Part of this study of the interaction of grain boundaries in alumina with an anorthite-based glassy phase is presented here.Previous systematic studies4 of different low-index surfaces of single crystal alumina showed that there is strong anisotropy in the faceting behavior of alumina and in the mobility of these facets in the presence of an anorthite-based glassy phase.
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Sheng, Huaping, He Zheng, Shuangfeng Jia, Lei Li, Fan Cao, Shujing Wu, Wei Han, Huihui Liu, Dongshan Zhao et Jianbo Wang. « Twin structures in CuO nanowires ». Journal of Applied Crystallography 49, no 2 (24 février 2016) : 462–67. http://dx.doi.org/10.1107/s1600576716001461.
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The structural characteristics of monoclinic CuO nanowires (NWs) fabricated by heating pure Cu in ambient air were investigated by electron microscopy. Besides the single-crystalline NW, four different twinned NWs with twinning planes of (11\bar 1), (002), (110) and {{(20\bar 2)}} have been found. The twin boundaries are generally in parallel with the NW axial direction. To the best of the authors' knowledge, the {{(11\bar 1)}} and (110) twins are reported for the first time in CuO. Moreover, the prevailing existence of {{(11\bar 1)}} and (002) twinned NWs could be closely related to the NW growth as well as the oxidation processes of Cu. The presented results provide a systematic investigation on the twin structures of CuO NWs, which may open up a pathway to explore new potential applications of CuO nanostructures.
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Fan, Lisha, Xiang Gao, Thomas O. Farmer, Dongkyu Lee, Er-Jia Guo, Sai Mu, Kai Wang et al. « Vertically Aligned Single-Crystalline CoFe2O4 Nanobrush Architectures with High Magnetization and Tailored Magnetic Anisotropy ». Nanomaterials 10, no 3 (5 mars 2020) : 472. http://dx.doi.org/10.3390/nano10030472.
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Micrometer-tall vertically aligned single-crystalline CoFe2O4 nanobrush architectures with extraordinarily large aspect ratio have been achieved by the precise control of a kinetic and thermodynamic non-equilibrium pulsed laser epitaxy process. Direct observations by scanning transmission electron microscopy reveal that the nanobrush crystal is mostly defect-free by nature, and epitaxially connected to the substrate through a continuous 2D interface layer. In contrast, periodic dislocations and lattice defects such as anti-phase boundaries and twin boundaries are frequently observed in the 2D interface layer, suggesting that interface misfit strain relaxation under a non-equilibrium growth condition plays a critical role in the self-assembly of such artificial architectures. Magnetic property measurements have found that the nanobrushes exhibit a saturation magnetization value of 6.16 μB/f.u., which is much higher than the bulk value. The discovery not only enables insights into an effective route for fabricating unconventional high-quality nanostructures, but also demonstrates a novel magnetic architecture with potential applications in nanomagnetic devices.
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Ou, Limin, Shengheng Nong, Ruoxi Yang, Yaoying Li, Jinrong Tao, Pan Zhang, Haifu Huang et al. « Multi-Role Surface Modification of Single-Crystalline Nickel-Rich Lithium Nickel Cobalt Manganese Oxides Cathodes with WO3 to Improve Performance for Lithium-Ion Batteries ». Nanomaterials 12, no 8 (12 avril 2022) : 1324. http://dx.doi.org/10.3390/nano12081324.
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Compared with the polycrystalline system, the single-crystalline ternary cathode material has better cycle stability because the only primary particles without grain boundaries effectively alleviate the formation of micro/nanocracks and retain better structural integrity. Therefore, it has received extensive research attention. There is no consistent result whether tungsten oxide acts as doping and/or coating from the surface modification of the polycrystalline system. Meanwhile, there is no report on the surface modification of the single-crystalline system by tungsten oxide. In this paper, multirole surface modification of single-crystalline nickel-rich ternary cathode material LiNi0.6Co0.2Mn0.2O2 by WO3 is studied by a simple method of adding WO3 followed by calcination. The results show that with the change in the amount of WO3 added, single-crystalline nickel-rich ternary cathode material can be separately doped, separately coated, and both doped and coated. Either doping or coating effectively enhances the structural stability, reduces the polarization of the material, and improves the lithium-ion diffusion kinetics, thus improving the cycle stability and rate performance of the battery. Interestingly, both doping and coating (for SC-NCM622-0.5%WO3) do not show a more excellent synergistic effect, while the single coating (for SC-NCM622-1.0%WO3) after eliminating the rock-salt phase layer performs the most excellent modification effect.
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Sarikaya, Mehmet, Ryoichi Kikuchi et I. A. Aksay. « Geometry and formation of twins in YBa2Cu3O7-x ». Proceedings, annual meeting, Electron Microscopy Society of America 46 (1988) : 852–53. http://dx.doi.org/10.1017/s0424820100106326.
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Geometry and formation of twins in the orthorhombic YBa2Cu3O7-x phase are studied by transmission electron microscopy and modeling. Samples with bulk superconductivity at 90K are produced by heating the stoichiometric 1:2:3 proportions of metal oxides with a single heat treatment schedule involving a heating rate of 5°C/min to 950°C (1 hr) and 1°C/min cooling to room temperature. Powder mixtures were formed by colloidal mixing of oxide powders or by molecular mixing techniques.Twinned domains with {110} twin boundaries, parallel to [001] of the orthorhombic lattice, usually form with both variants occurring in a single grain (Fig. 1). The twin boundary separation λ (Fig. 2) is dictated by energetic and geometrical requirements which are both related to Δa = b — a, where b and a are lattice parameters of the orthorhombic phase. Geometrical requirements lead to the estimate that the stable values of λ are integer values of the basic distance d.
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Daneu, Nina, Goran Dražič, Matjaž Mazaj, Fabrice Barou et José Alberto Padrón-Navarta. « Formation of contact and multiple cyclic cassiterite twins in SnO2-based ceramics co-doped with cobalt and niobium oxides ». Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 78, no 4 (27 juillet 2022) : 695–709. http://dx.doi.org/10.1107/s2052520622006758.
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Contact and multiple cyclic twins of cassiterite commonly form in SnO2-based ceramics when SnO2 is sintered with small additions of cobalt and niobium oxides (dual doping). In this work, it is shown that the formation of twins is a two-stage process that starts with epitaxial growth of SnO2 on CoNb2O6 and Co4Nb2O9 seeds (twin nucleation stage) and continues with the fast growth of (101) twin contacts (twin growth stage). Both secondary phases form below the temperature of enhanced densification and SnO2 grain growth; CoNb2O6 forms at ∼700°C and Co4Nb2O9 at ∼900°C. They are structurally related to the rutile-type cassiterite and can thus trigger oriented (epitaxial) growth (local recrystallization) of SnO2 domains in different orientations on a single seed particle. While oriented growth of cassiterite on columbite-type CoNb2O6 grains can only result in the formation of contact twins, the Co4Nb2O9 grains with a structure comparable with that of corundum represent suitable sites for the nucleation of contact and multiple cyclic twins with coplanar or alternating morphology. The twin nucleation stage is followed by fast densification accompanied by significant SnO2 grain growth above 1300°C. The twin nuclei coarsen to large twinned grains as a result of the preferential and fast growth of the low-energy (101) twin contacts. The solid-state diffusion processes during densification and SnO2 grain growth are controlled by the formation of point defects and result in the dissolution of the twin nuclei and the incorporation of Nb5+ and Co2+ ions into the SnO2 matrix in the form of a solid solution. In this process, the twin nuclei are erased and their role in the formation of twins is shown only by irregular segregation of Co and Nb to the twin boundaries and inside the cassiterite grains, and Co,Nb-enrichment in the cyclic twin cores.
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Carey, M. J., F. E. Spada, A. E. Berkowitz, W. Cao et G. Thomas. « Preparation and structural characterization of sputtered CoO, NiO, and Ni0.5Co0.5O thin epitaxial films ». Journal of Materials Research 6, no 12 (décembre 1991) : 2680–87. http://dx.doi.org/10.1557/jmr.1991.2680.
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Single phase CoO, NiO, and Ni0.5Co0.5O epitaxial films have been prepared by reactive sputtering onto 〈0001〉 α−Al2O3 substrates maintained at 373 K. Epitaxy was confirmed by x-ray diffraction (XRD) and high resolution electron microscopy (HREM) techniques. XRD experiments indicate that these monoxide films are cubic and contain rotation twins with the twin axis parallel to 〈111〉. Lattice parameters for the CoO and NiO films are 0.4254 ± 0.0001 nm and 0.4173 ± 0.0006 nm, respectively, and agree with published values for the corresponding bulk oxides. The lattice parameter 0.4220 ± 0.0001 nm for the Ni0.5Co0.5O film lies between those of CoO and NiO and suggests that the mixed oxide film is compositionally homogeneous. Cross-sectional HREM images of the Ni0.5Co0.5O specimen show Σ3(12) twin boundaries perpendicular to the oxide-substrate interface. The twin regions are approximately 30 nm in size and are uniformly distributed throughout the film. The epitaxial orientation of the monoxide films with respect to the substrate can be summarized by the relationships [111] monoxide // [0001] α−Al2O3, [10] monoxide // [100] α−Al2O3, and [11] monoxide // [110] α−Al2O3.
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Ramamurthy, Sundar, Brian C. Hebert et C. Barry Carter. « Olivine-MgO interfaces produced by crystallization of glass fulms on single-crystal MgO substrates ». Proceedings, annual meeting, Electron Microscopy Society of America 53 (13 août 1995) : 342–43. http://dx.doi.org/10.1017/s0424820100138087.
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Glassy silicates are present at grain boundaries in almost all liquid-phase sintered ceramic oxides. In many cases, the amorphous-crystalline interfaces in the sintered microstructure can be modified by inducing crystallization of the glassy phase. The intergranular phases in polycrystalline MgO are typically silicates with cations of calcium, magnesium and iron in the silicate network. A systematic approach to study the crystallization behavior of glass-MgO interfaces has been attempted in the present study. Following the work by Mallamaci in which crystallization of a silicate glass in contact with A12O3 was studied, devitrification of glass in contact with single-crystal MgO has been investigated. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to characterize the resulting microstructures.A pellet of Mg2SiO4 (forsterite) prepared by hot-pressing MgO and SiO2 powders was used as the target for depositing glass films onto single-crystal MgO substrates by pulsed-laser deposition (PLD). Glass films with the composition of olivine.
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Wang, Z. L., Z. W. Pan et Z. R. Dai. « Structures of Oxide Nanobelts and Nanowires ». Microscopy and Microanalysis 8, no 6 (décembre 2002) : 467–74. http://dx.doi.org/10.1017/s1431927602010383.
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We have recently reported the synthesis of one-dimensional nanobelt structures of ZnO, SnO2, In2O3, CdO, Ga2O3, and PbO2 by evaporating the desired commercial metal oxide powders at high temperatures (Science (2001), 291, 1947). The as-synthesized oxide nanobelts are pure, structurally uniform, single crystalline, and most of them free from dislocations. The beltlike morphology appears to be a unique and common structural characteristic for the family of semiconducting oxides. In the present article, we focus on the twin and stacking fault planar defects found in oxide nanobelts and nanowires although they are rarely observed. Some interesting and unique growth morphologies are presented to illustrate the roles played by surface energy and kinetics in growth. It is shown that the surfaces of the oxide nanobelts are enclosed by the low-index, low-energy crystallographic facets. The growth morphology is largely dominated by the growth kinetics.
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Ávila, Carlos Fernando, Leonardo Lagoeiro, Paola Ferreira Barbosa et Leonardo Graça. « EBSD analysis of rhombohedral twinning in hematite crystals of naturally deformed iron formations ». Journal of Applied Crystallography 48, no 1 (30 janvier 2015) : 212–19. http://dx.doi.org/10.1107/s1600576714025928.
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The rhombohedral twinning in hematite has an important role in the accommodation of the deformation of hematite single crystals and hematite aggregates. It is a contact twinning and occurs as lamellae parallel to the \{10{\overline 1}2\} planes of hematite as a result of twin gliding on such planes. On account of the recent applications of electron backscatter diffraction (EBSD) techniques in a wide range of microstructural studies, the determination of symmetry operations that relate crystals in a deformed crystalline aggregate is crucial for the full textural characterization. This study presents an EBSD-based crystallographic analysis of the rhombohedral twinning on hematite crystals of a naturally deformed banded iron formation. Manipulations of theoretical pole figures depicting the symmetry relation of the rhombohedral twinning and misorientation and crystallographic data obtained by EBSD are used to establish the rotational relationship between twin and parent crystals. A method for determining pairs of axes and angles of rotation was developed which can be extended to any other twin laws or misorientation patterns in any other crystal system. It was found that the hematite rhombohedral twins are related to the parent crystal by an approximately 85° rotation about the 〈02{\overline 2}1〉 directions. Hence it could be determined that this consists of a macroscopic twinning element which is an alternative to the conventional ones used to describe the symmetry of the twin. It also matches microscopic twinning elements for the rhomb twinning law. Additionally, this method allows the determination of the crystallographic orientation of the twin lamellae and which particular 〈02{\overline 2}1〉 axis satisfies the 85°〈02{\overline 2}1〉 pair of rotation. The use of an unambiguous angle–axis pair of rotation allows the identification of twin boundaries in complex and finely grained aggregates and the distinction of twinning laws in a particular crystal.
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Moriyama, Takumi, Takahiro Yamasaki, Takahisa Ohno, Satoru Kishida et Kentaro Kinoshita. « Formation Mechanism of Conducting Path in Resistive Random Access Memory by First Principles Calculation Using Practical Model Based on Experimental Results ». MRS Advances 1, no 49 (2016) : 3367–72. http://dx.doi.org/10.1557/adv.2016.461.
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ABSTRACTFor practical use of Resistive Random Access Memory (ReRAM), understanding resistive switching mechanism in transition metal oxides (TMO) is important. Some papers predict its mechanism by using first principles calculation; for example, TMO become conductive by introducing oxygen vacancy in bulk single crystalline TMO. However, most of ReRAM samples have polycrystalline structures. In this paper, we introduced a periodic slab model to depict grain boundary and calculated the surface energy and density of states for surfaces of NiO with various orientations using first-principles calculation to consider the effect of grain boundaries for resistive switching mechanisms of ReRAM. As a results, vacancies can be formed on the side surface of grain more easily than in grain. Moreover, we showed that surface conductivity depends on surface orientation of NiO and the orientation of side surface of grain can change easily by introduction of vacancies, which is the switching mechanism of NiO-ReRAM
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Murshed, M. Mangir, Pei Zhao, Evgeny Alekseev, Ashfia Huq et Thorsten Gesing. « Lattice thermal expansion of complex oxides with intrinsic anharmonicity ». Acta Crystallographica Section A Foundations and Advances 70, a1 (5 août 2014) : C161. http://dx.doi.org/10.1107/s2053273314098386.
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The lattice thermal expansion of crystalline solids cannot be adequately modeled by Grüneisen approximation using either Einstein single harmonic frequency or Debye frequency spectrum because a true phonon spectrum does not follow either of the two kinds. The Debye model misfits to many observations due to the fact that real solids comprises of axial anisotropy, lattice waves with dispersion at the Brillouin zone boundaries, low/high frequency optical vibrations in excess of the Debye spectrum. The actual frequency distribution is a complicated function of frequency instead of a simple parabolic Debye spectrum. The frequency distribution can be simplified using power series [1] leading to singularities before and after the Debye cutoff frequency. Using multiple Debye or Einstein oscillators, or their mixtures, is also common practice to better describe the lattice expansion, however, these models extremely suffer from intrinsic anharmonicity in particular at high temperatures. It was demonstrated that even the noble monoatomic solids required inclusion of anharmonic terms in the harmonic model to better explain the observed values [2]. Worse even, when anharmonicity becomes dominant due to formation of vacancies and defects, anomalies of hard/soft modes or change of stereochemical activities of lone electron pairs (LEPs) as function of temperature. Herein we approach an extended Grüneisen approximation that includes harmonic, quasiharmonic and intrinsic anharmonic potentials to describe the internal energy of the crystal as function of temperature. The model has been applied to several complex oxides with LEPs (Bi2Ga4O9[3]) along with axial negative thermal expansion (PbFeBO4) and rigid-unit-modes (KAsW2O9) reported here. The metric parameters were obtained from quality data collected from temperature-dependent neutron and X-ray powder diffractions.
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Das, Dhrubajyoti, Sanchita Manna et Sreeraj Puravankara. « Electrolytes, Additives and Binders for NMC Cathodes in Li-Ion Batteries—A Review ». Batteries 9, no 4 (24 mars 2023) : 193. http://dx.doi.org/10.3390/batteries9040193.
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Among the current battery technologies, lithium-ion batteries (LIBs) are essential in shaping future energy landscapes in stationary storage and e-mobility. Among all components, choosing active cathode material (CAM) limits a cell’s available energy density (Wh kg−1), and the CAM selection becomes critical. Layered Lithium transition metal oxides, primarily, LiNixMnyCozO2 (NMC) (x + y + z = 1), represent a prominent class of cathode materials for LIBs due to their high energy density and capacity. The battery performance metrics of NMC cathodes vary according to the different ratios of transition metals in the CAM. The non-electrode factors and their effect on the cathode performance of a lithium-ion battery are as significant in a commercial sense. These factors can affect the capacity, cycle lifetime, thermal safety, and rate performance of the NMC battery. Additionally, polycrystalline NMC comprises secondary clusters of primary crystalline particles prone to pulverization along the grain boundaries, which leads to microcrack formation and unwanted side reactions with the electrolyte. Single-crystal NMC (SC-NMC) morphology tackles the cycling stability issue for improved performance but falls short in enhancing capacity and rate capability. The compatibility of different combinations of electrolytes and additives for SC-NMC is discussed, considering the commercial aspects of NMC in electric vehicles. The review has targeted the recent development of non-aqueous electrolyte systems with various additives and aqueous and non-aqueous binders for NMC-based LIBs to stress their importance in the battery chemistry of NMC.
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Walker, F. J., R. A. Mckee, S. J. Pennycook et T. G. Thundat. « Defects and Their Origin in Thin Films of (001) Alkaline Earth Oxides ». MRS Proceedings 401 (1995). http://dx.doi.org/10.1557/proc-401-13.
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AbstractMgO is used as an optical isolation layer for waveguides epitaxially grown on silicon. The crystalline perfection of MgO is a critical issue because it serves as a substrate for the single crystal, perovskite guiding layer. Imperfections in the MgO will result in imperfections in the guiding layer and lead to large optical losses for the planar waveguide structure. We show that the most common defect to form in thin films of MgO are twin boundaries between {111}-type planes. The highest density of twins is observed when (001) MgO is grown directly on silicon/MgO interlayers containing barium. Twinning is shown to accommodate the large size of barium impurities incorporated in the MgO films through the formation of internal grain boundaries and open surfaces other than the growing (001) of MgO.
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Mesnier, Alex, et Arumugam Manthiram. « Influence of Single-Crystalline Morphology on the Electrochemical Behavior of High-Nickel Layered Oxide Cathodes ». Journal of The Electrochemical Society, 2 août 2023. http://dx.doi.org/10.1149/1945-7111/aceca6.
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Abstract High-nickel layered oxides are being pursued for their high specific capacities. With increasing nickel content, the layered oxides also suffer from structural and morphological instabilities, which degrade the electrochemical performance. Single-crystalline morphology presents an attractive solution to these problems, simultaneously reducing surface area available for parasitic reactions and preventing electrolyte penetration into the bulk with the removal of grain boundaries. Single-crystal cathodes have already shown promising results with NMC composition cathodes, but there are still gaps in the fundamental understanding of how single-crystalline morphology alters electrochemical behavior. We attempt to fill some of these gaps by studying in detail the electrochemical operation of polycrystalline and single-crystalline LiNiO¬2 (LNO). Single-crystal LNO is prepared through a molten salt method yielding high-quality, distinct crystals with comparable lattice chemistry to polycrystalline LNO. The single-crystal LNO achieves far greater stability during long-term cycling, reaching 500 cycles with 82.5% capacity retention. Interestingly, the single-crystalline LNO also displays superior rate performance, delivering 157 mA h g-1 at 10C discharge rate. Investigation of the phase evolution behavior during cycling strongly suggests that the absence of grain boundaries in single-crystalline LNO is responsible for the superior performance.
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Zhang, Minjie, Jiating Wu, Ke Shi, Langsheng Ling, Wei Tong, Chuanying Xi, Li Pi, J. Wosnitza, Huiqian Luo et Zhaosheng Wang. « Huge magnetostriction in superconducting single-crystalline BaFe1.908Ni0.092As2 ». Applied Physics Letters 123, no 7 (14 août 2023). http://dx.doi.org/10.1063/5.0166209.
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The performance of iron-based superconductors in high magnetic fields plays an important role for their practical application. In this work, we measured the magnetostriction and magnetization of BaFe1.908Ni0.092As2 single crystals using pulsed magnetic fields up to 60 T and static magnetic fields up to 33 T, respectively. A huge longitudinal magnetostriction (of the order of 10–4) was observed in the direction of twin boundaries. The magnetization measurements evidence a high critical-current density due to strong bulk pinning. By using magnetization data with an exponential flux-pinning model, we can reproduce the magnetostriction curves qualitatively. This result shows that the magnetostriction of BaFe1.908Ni0.092As2 can be well explained by a flux-pinning-induced mechanism.
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Findikoglu, Alp, Terry G. Holesinger, Alyson Niemeyer, Vladimir Matias et Ozan Ugurlu. « Aligned-Crystalline Si Films on Non-Single-Crystalline Substrates ». MRS Proceedings 1150 (2008). http://dx.doi.org/10.1557/proc-1150-rr03-05.
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AbstractWe summarize recent progress in growth and characterization of aligned-crystalline silicon (ACSi) films on polycrystalline metal and amorphous glass substrates. The ACSi deposition process uses, as a key technique, ion-beam-assisted deposition (IBAD) texturing on a non-single-crystalline substrate to achieve a biaxially-oriented (i.e., with preferred out-of-plane and in-plane crystallographic orientations) IBAD seed layer, upon which homo- and hetero-epitaxial buffer layers and hetero-epitaxial silicon (i.e., ACSi) films with good electronic properties can be grown. We have demonstrated the versatility of our approach by preparing ACSi films on customized architectures, including fully insulating and transparent IBAD layer and buffer layers based on oxides on glass and flexible metal tape, and conducting and reflective IBAD layer and buffer layers based on nitrides on flexible metal tape. Optimized 0.4-μm-thick ACSi films demonstrate out-of-plane and in-plane mosaic spreads of 0.8° and 1.3°, respectively, and a room-temperature Hall mobility of ∼90 cm2/V.s (∼50% of what is achievable with epitaxial single-crystalline Si films, and ∼1000 times that of amorphous Si films) for a p-type doping concentration of ∼4×1016 cm−3. By using various experimental techniques, we have confirmed the underlying crystalline order and the superior electrical characteristics of low-angle (<5°) grain boundaries in ACSi films. Forming gas anneal experiments indicate that Si films with low-angle grain boundaries do not need to be passivated to demonstrate improved majority carrier transport properties. Measurements on metal-insulator-semiconductor structures using ACSi films yield near-electronic-grade surface properties and low surface defect densities in the ACSi films. A prototype n+/p/p+–type diode fabricated using a 4.2-μm-thick ACSi film shows minority carrier lifetime of ∼3 μs, an estimated diffusion length of ∼30 μm in the p-Si layer with a doping concentration of 5×1016 cm−3, and external quantum efficiency of ∼80% at 450 nm with the addition of an MgO film anti-reflector.
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Choi, Young Chul, Dong Jae Bae, Seung Mi Lee, Young Soo Park, Young Hee Lee, Gyeong-Su Park, Won Bong Choi, Nae Sung Lee et Jong Min Kim. « ARC Discharge for the Synthesis of Monoclinic Ga2O3 Nanowires ». MRS Proceedings 581 (1999). http://dx.doi.org/10.1557/proc-581-239.
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ABSTRACTMonoclinic gallium oxide (β-Ga2O3) nanowires were catalytically synthesized by electric arc discharge of GaN powders mixed with a small amount (less than 5 %) of transition metals under a pressure of 500 Torr (80 %-Ar + 20 %-O2). Scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM) images showed that the average diameter of the wires were about 30 nm and their lengths were as long as up to one hundred micrometer, resulting in extremely large aspect ratio. Fourier diffractogram was indicative of single crystalline nature of the β-Ga2O3 wire. HRTEM image also showed β-Ga2O3 with twin defects at the center of the wire which might play as nucleation seeds. Both X-ray diffraction (XRD) patterns and FT-Raman spectra of the wires identified the observed nanowires as monoclinic crystalline gallium oxides.
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Gao, Y., K. L. Merkle, H. L. M. Chang, T. J. Zhang et D. J. Lam. « Electron Microscopy Study Of Mocvd-Grown Tio2Thin Films and Tio2/Al203 Interfaces ». MRS Proceedings 209 (1990). http://dx.doi.org/10.1557/proc-209-685.
Texte intégralRésumé :
ABSTRACTTiO2 thin films grown on (1120) sapphire at 800°C by the MOCVD technique have been characterized by transmission electron microscopy. The TiO2 thin films are single crystalline and have the rutile structure. The epitaxial orientation relationship between the TiO2 thin films (R) and the substrate (S) has been foundto be: (101)[010]R║(1l20)[0001]s. Growth twins in the films are commonly observed with the twin plane{101} and twinning direction <011>. Detailed atomic structures of the twin boundaries and TiO2/α-Al203 interfaces have been investigated by highresolution electron microscopy (HREM).When the interfaces are viewed in the direction of [010]R/[000l]S, the interfaces are found to be structurally coherent in the direction of [1Ol]R/[1100]s,in which the lattice mismatch at the interfaces is about 0.5%.
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Chen, Xiang, Shayuan Weng, Xing Yue, Tao Fu et Xianghe Peng. « Effects of Anisotropy and In-Plane Grain Boundary in Cu/Pd Multilayered Films with Cube-on-Cube and Twinned Interface ». Nanoscale Research Letters 16, no 1 (28 avril 2021). http://dx.doi.org/10.1186/s11671-021-03528-9.
Texte intégralRésumé :
AbstractIn crystalline materials, grain boundary and anisotropy of crystal structure affect their mechanical properties. The effects of interfacial structure on the mechanical properties may be diverse when the multilayer film is loaded along different directions. In this work, we performed a series of molecular dynamics simulations of the tension of in-plane single and polycrystalline Cu/Pd multilayered films with cube-on-cube (COC) and twinned interfaces to explore the effects of the interfacial structure, loading direction and in-plane grain boundaries on their mechanical properties. The interfacial misfit dislocation lines become bent after relaxation, and the high temperature of 300 K was found as a necessary condition. When stretched along 〈110〉 direction, the strengthening effect of the COC interface is more noticeable; however, when stretched along 〈112〉 direction, the twin interface's strengthening effect is more visible, showing the anisotropic effect of interfacial structure on mechanical properties. However, in the in-plane honeycomb polycrystalline sample, the twin interface showed a pronounced strengthening effect, and no jogged dislocations were observed.
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Matsunani, Hiroyuki, Tetsuzo Ueda et Hironori Nishino. « Step-Controlled Epitaxial Growth of SiC ». MRS Proceedings 162 (1989). http://dx.doi.org/10.1557/proc-162-397.
Texte intégralRésumé :
ABSTRACTVapor phase epitaxial(VPE) growth of SIC on 6H-SiC substrates has been carried out at 1500°C or below. On well-oriented (0001)Si faces, twin crystalline 3C-SiC with double positioning boundaries was grown, whereas on off-oriented (0001)Si faces, single crystalline 6H-SiC was grown with a very smooth surface. This temperature is more than 300°C lower in comparison with that for 6H-SiC VPE growth reported previously. By the introduction of offorientation, the density of surface steps is increased. Crystal growth occurs through lateral growth from the steps. The surface morphology of grown layers on off-oriented substrates, however, varied with the offdirection and the polarity of substrates. Grown layers are characterized by etch-pits observation, photoluminescence(PL) measurements and reflection high energy electron diffraction. On the basis of these experimental results, the growth mechanism on (0001)Si and (0001)C faces of 6H-SiC is discussed. P-type doping is tried, and electrical and PL properties are examined. Pn junction fabrication is also studied.