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Albering, Jörg H., i Wolfgang Jeitschko. "Quaternary Thorium Transition Metal Pnictide Oxides: ThCu1-xPO, ThCuAsO, and Th2Ni3-xP3O". Zeitschrift für Naturforschung B 51, nr 2 (1.02.1996): 257–62. http://dx.doi.org/10.1515/znb-1996-0215.
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Abstract The new compounds ThCu1-xPO and ThCuAsO with ZrCuSiAs-type structure were prepared in well crystallized form by chemical vapor transport reactions. Th2Ni3-xP3O with a new structure type was obtained by reaction of ThO2 with the other elemental components in an alumina crucible at high temperatures. The crystal structures of the three compounds were determined from single-crystal X-ray data. ThCu1-xPO: P4/nmm, a = 389.43(4), c -828.3(1) pm, R = 0.024 for 13 variable parameters and 338 structure factors; ThCuAsO: P4/ nmm, a = 396.14(5), c = 844.0(1) pm, R = 0.028 (13 variables and 379 F values); Th2Ni3-xP3O : P4/nmm, a = 394.62(4), c = 1723.2(3) pm, R = 0.018 (27 variables and 374 F values). The refinement of the occupancy parameters revealed significant deviations from the ideal values for the transition metal sites for two compounds resulting in the exact compositions ThCu0.938(4)PO and Th2Ni2.45(1)P3O . Magnetic susceptibility measurements indicate Pauli paramagnetism for ThCu1-xPO . The crystal structures of these compounds are closely related. They belong to a large family of tetragonal structures of which the ThCr2Si2-and the PbFCl-type structures are well known examples.
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Toriyama, T., T. Konishi i Y. Ohta. "Anomalous electronic structures of transition-metal oxides with hollandite-type crystal structure". Journal of Physics: Conference Series 391 (14.12.2012): 012109. http://dx.doi.org/10.1088/1742-6596/391/1/012109.
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Ильинский, А. В., i Е. Б. Шадрин. "Закономерности формирования электропроводящих свойств окислов ряда Магнели". Физика твердого тела 65, nr 3 (2023): 460. http://dx.doi.org/10.21883/ftt.2023.03.54746.536.
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The hybridization of vanadium ions and oxygen ions is considered for four vanadium oxides included in the Magneli series: VO, V2O3, VO2, V2O5. Based on the data on hybridization, the details of the structure of the crystal lattice of these oxides are analyzed. For each oxide, the role of electrons not participating in the stabilization of the crystal frame in the process of the semiconductor-metal phase transition was revealed. The complex Mott-Peierls character of the phase transitions in all the listed strongly correlated compounds has been established. It is shown that as the degree of oxidation of the V atom increases, the numerical value of the metallic conductivity of the high-temperature phase naturally decreases and, simultaneously, the temperature of the phase transition from the semiconductor to the metallic state increases. Keywords: phase transitions, Magneli series, electron correlations, hybridization of atomic orbitals.
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Ilinskiy A.V. i Shadrin E.B. "Patterns of formation of electrically conductive properties of oxides of the Magneli series". Physics of the Solid State 65, nr 3 (2023): 450. http://dx.doi.org/10.21883/pss.2023.03.55588.536.
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The hybridization of vanadium ions and oxygen ions is considered for four vanadium oxides included in the Magneli series: VO, V2O3, VO2, V2O5. Based on the data on hybridization, the details of the structure of the crystal lattice of these oxides are analyzed. For each oxide, the role of electrons not participating in the stabilization of the crystal frame in the process of the semiconductor-metal phase transition was revealed. The complex Mott-Peierls character of the phase transitions in all the listed strongly correlated compounds has been established. It is shown that as the degree of oxidation of the V atom increases, the numerical value of the metallic conductivity of the high-temperature phase naturally decreases and, simultaneously, the temperature of the phase transition from the semiconductor to the metallic state increases. Keywords: phase transitions, Magneli series, electron correlations, hybridization of atomic orbitals.
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Su, D. S., E. Zeitler i R. Schlögl. "Structure Changes in Transition Metal Oxides Induced During Electron Microscopy". Microscopy and Microanalysis 7, S2 (sierpień 2001): 1096–97. http://dx.doi.org/10.1017/s143192760003155x.
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Many catalytic materials, especially the maximum valence transition metal oxides, are particularly susceptible to electron beam irradiation and thus undergo structural changes. Hence knowledge about the behaviour of catalytic materials under the electron beam is of importance for all TEM investigations of such materials. On the other hand, this effect can be utilised for an in-situ study of the reductive property, phase transition and/or phase stability of various transition metal oxides in an inert, simple ambient high-vacuum. The knowledge so obtained is needed for understanding the reduction mechanism of catalysts in more complicated chemical environments. in the present work, we study the electron beam induced change in MoO3 and TiO2 (anatase) by means of electron energy-loss spectroscopy (EELS), electron diffraction and high-resolution electron microscopy (HREM).Molybdenum trioxide, MoO3, important as catalyst in the selective oxidation of hydrocarbons, forms an orthorhombic crystal layer structure. Fig. 1 shows oxygen AT-edges recorded at various irradiation periods in a Philips 200 FEG electron microscope.
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Tatsumi, Kazuyoshi, Shunsuke Muto i Ján Rusz. "Energy Loss by Channeled Electrons: A Quantitative Study on Transition Metal Oxides". Microscopy and Microanalysis 19, nr 6 (29.08.2013): 1586–94. http://dx.doi.org/10.1017/s1431927613013214.
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AbstractElectron energy-loss spectroscopy (EELS) attached to current transmission electron microscopes can probe not only element-selective chemical information, but also site-selective information that depends on the position that a specific element occupies in a crystal lattice. The latter information is exploited by utilizing the Bloch waves symmetry in the crystal, which changes with its orientation with respect to the incident electron wave (electron channeling). We demonstrate the orientation dependence of the cross-section of the electron energy-loss near-edge structure for particular crystalline sites of spinel ferrites, by quantitatively taking into account the dynamical diffraction effects with a large number of the diffracted beams. The theoretical results are consistent with a set of experiments in which the transition metal sites in spinel crystal structures are selectively excited. A new measurement scheme for site-selective EELS using a two-dimensional position-sensitive detector is proposed and validated by theoretical predictions and trial experiments.
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Choi, Woo-Seok, Nak Kyun Sung i Jeom-Soo Kim. "Enhancing Cycle Performance for Li-Rich Layered Oxides By the Stabilization of Crystal Structure". ECS Meeting Abstracts MA2022-02, nr 7 (9.10.2022): 2539. http://dx.doi.org/10.1149/ma2022-0272539mtgabs.
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Li-rich layered oxides (LLO) have been studied as a next generation low-cost and high-capacity positive electrode materials. In LLO, the structural stability must be ensured to reversible Li intercalation. Blocking the tetrahedral site, the path of ions moving from transition metal sites to the lithium layer, may reduce the cation mxing which casuses the structural instability. In addition, introducing electrochemically inactive metal ions in the transition metal layer would stabilize the O-Me-O stacking by binding energy with oxygen which is higher than the transition metals. In this study, LLOs were obtained with and without doping at varous conditions. Doping elements are B and Ge of x mol% with repect of transition metals (Mn, Ni, Co). The effect of doping of is evaluated through the evaluation of the physical and electrochemical characteristics of the synthesized LLOs. Especially, the elelctrochemical cycle stability is throughly studied at various charge cuf-off voltages. The details of evaluation and analysis results will be presented.
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McCartney, M. R. "Electron-beam-induced 3-D epitaxy Of TiO on TiO2". Proceedings, annual meeting, Electron Microscopy Society of America 46 (1988): 684–85. http://dx.doi.org/10.1017/s0424820100105485.
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It is well-known that the surfaces of maximally-valent transition-metal oxides should be particularly susceptible to electron-stimulated desorption of oxygen under the conditions prevailing in high-resolution electron microscopy (HREM). Indeed, it has been observed that lattice fringes corresponding to TiO have developed on the surfaces of crystals of rutile, TiO2. Fig. 1a shows the modified surface of a rutile crystal tilted to (001)-projection with extensive regions of disorder and small crystallites of reduced (metallic) oxide at the edge; fig. 1b shows TiO2 in a [010]-projection with crystals of TiO in -projection. By combining the techniques of high-resolution imaging, optical diffractogram (ODM) analysis, and computer modeling of crystal structure, a three-dimensional epitaxy for the growth of TiO on TiO2 can be proposed.
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Romanenko, A. I., G. E. Chebanova, Tingting Chen, Wenbin Su i Hongchao Wang. "Review of the thermoelectric properties of layered oxides and chalcogenides". Journal of Physics D: Applied Physics 55, nr 14 (3.12.2021): 143001. http://dx.doi.org/10.1088/1361-6463/ac3ce6.
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Abstract The current state of investigation on thermoelectric properties of layered chalcogenides and oxides is considered. The relationship between the quasi-two-dimensionality of electronic transport properties and thermoelectric properties is confirmed. A decrease in the dimension of electron transport from three-dimensional to quasi-two-dimensional in materials with a layered structure increases the thermopower with a slight change in electrical conductivity. The bismuth tellurides, bismuth selenides and its alloys are currently one of the outstanding state of the art bulk thermoelectric materials with layered structure. Layered transition metal dichalcogenides MX2 (M is a transition metal, X is a chalcogen) are efficient thermoelectric materials at higher temperatures (500–800 K). In these materials, an increase in thermoelectric properties associated with the two-dimensionalization of electron transport is also observed. Layered monochalcogenides MX (M = Sn, Pb, Ge; X = S, Se, Te) are also a promising class of thermoelectric materials. In SnSe single crystals, Z T ∼ 2.6 is obtained at 923 K due to the very low thermal conductivity along the b axis (0.23 W (m K)−1 at 973 K). Layered chalcogenides CuCrX2 (X = S, Se, Te) containing magnetic Cr atoms are effective thermoelectrics at higher temperatures (up to 800 K) due to the presence of phonon glass–electron crystal state led to a significant decrease in thermal conductivity at high temperatures. Magnetic atoms in CuCrX2 compounds lead to the presence of magnetic phase transitions affecting their thermoelectric properties. Interest in oxide-based thermoelectric materials has significantly increased due to their stability in air and higher temperatures for maximum efficiency. The most promising thermoelectric oxide materials Ca3Co4O9, Na x CoO2, Bi2Ca2Co2O x , and CaCo2O4 have a layered structure and contain magnetic Co atoms leading to magnetic ordering and influence on thermoelectric properties. The presence of phase transitions affects the thermoelectric parameters of thermoelectrics and the thermoelectric figure of merit ZT.
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Fabrykiewicz, Piotr, Radosław Przeniosło, Izabela Sosnowska i François Fauth. "Positive and negative monoclinic deformation of corundum-type trigonal crystal structures of M 2O3 metal oxides". Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 74, nr 6 (21.11.2018): 660–72. http://dx.doi.org/10.1107/s2052520618014968.
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The crystal structures of several transition metal oxides, Ti2O3, V2O3, Cr2O3, Al2O3 and α-Fe2O3, are studied using synchrotron radiation X-ray powder diffraction. The observed angular dependence of the integral breadths is described by two models: (i) the distorted corundum-type structure model described by the space group C2/c and (ii) the Stephens model of anisotropic Bragg peak broadening. These two models are shown to be equivalent. Ti2O3, V2O3 and Cr2O3 show a `positive' distortion which is related to the possible metal–metal bond suggested by Goodenough in the literature (the deformation leads to shorter metal–metal distances) whereas Al2O3 and α-Fe2O3 show a `negative' distortion which leads to relatively longer metal–metal distances.
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Pan, Pei, Ting Wang, Lihui Chen, Feng Wang, Xiong Yang, Caiqin Qin i Yu Ding. "Crystal-seeds induced construction of ZnO–ZnFe2O4 micro-cubic composites as excellent anode materials for lithium ion battery". RSC Advances 8, nr 29 (2018): 16187–92. http://dx.doi.org/10.1039/c8ra01785a.
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This work aims at designing a fine assembly of two different transition metal oxides with a distinct band-gap energy into a bi-component-active hetero-structure to improve electrochemical performance.
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Kan, Er Jun. "Electronic Structures in LaTiO3/LaAlO3 Multilayers". Advanced Materials Research 771 (wrzesień 2013): 7–11. http://dx.doi.org/10.4028/www.scientific.net/amr.771.7.
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We demonstrate the existence of a hidden degree of freedom controlling the orbitalordering in [LaTiO1/[LaAlO5 multilayers with comprehensive density-functional theorycalculations. The orbitals of two-dimensional (2D) 3d1state of Ti atoms in the multilayers alwayscontain large dxy components, which is unexpected from crystal field theory (first Jahn-Tellerdistortion). The competition between first and second Jahn-Teller distortion induces variousmagnetic properties. Thus, transition-metal oxides/non-transition-metal oxides multilayers mayprovide an important direction to manipulate the spin and orbital ordering in magnetic materials.
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Moshkina E. M., Molokeev M. S., Eremin E. V. i Bezmaternykh L. N. "Influence of Ga-substitution to the structural and magnetic properties of (Mn,Fe)-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=- bixbyite". Physics of the Solid State 65, nr 6 (2023): 1009. http://dx.doi.org/10.21883/pss.2023.06.56116.57.
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To study the dependence of the properties of ternary oxides (Mn,Fe,Ga)2O3 with the bixbyite structure on the composition, the temperature dependences of the magnetization and ac magnetic susceptibility of two single-crystal samples of different compositions obtained using the flux method were analyzed. A detailed study of the structure was carried out using single-crystal X-ray diffraction analysis, and the changes in structural parameters depending on the composition were analyzed. The dc magnetization and ac magnetic susceptibility of Fe1.1Mn0.76Ga0.14O3 and Fe0.65Mn1.1Ga0.26O3 bixbyites have been studied. Despite the qualitatively similar behavior of the magnetic properties, significant differences were also found, despite a small difference in the Mn/Fe/Ga ratio in the samples under study. It is shown that both compounds experience two successive low-temperature magnetic phase transitions from the paramagnetic phase at T=20-32 K as the temperature is lowered. Calculations of the Mydosh parameter for the detected phase transitions showed different degrees of ordering in the compounds under study. Keywords: transition metal oxides, magnetic phase transitions, spin glass state, bixbyite.
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Zuo, Wenhua, Guiliang Xu i Khalil Amine. "The Air Stability of Sodium Layered Oxide Cathodes". ECS Meeting Abstracts MA2022-02, nr 7 (9.10.2022): 2594. http://dx.doi.org/10.1149/ma2022-0272594mtgabs.
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Sodium-ion batteries (NIBs) are listed as one of the ideal alternatives for lithium-ion batteries (LIBs), due to the abundant sodium resources, cost-effective electrode materials of NIBs, and same architecture of NIBs to LIBs. To enable the practical implementation of NIBs, advanced cathodes with higher energy/power densities, better safety and cycle life, as well as lower cost are required. Layered lithium transition metal oxides (LiTMO2) are one of the most successful cathode materials for commercial LIBs. Similarly, layered sodium transition metal oxides (NaxTMO2, also termed as sodium layered oxides) are of particular interest for commercial NIBs owing to their high specific capacity, a wide variety of redox-active elements, and the possibility for the manufacturers to employ established synthesis processes as their lithium counterparts. Sodium layered oxides are built up by ordered stacking of alternate alkali-metal (Na+) layers and transition metal layers (TmO2). The two-dimensional structure makes them the natural hosts for alkali-metal ions and other ions or small molecules, such as H2O. Therefore, when exposed to moist atmospheres, layered oxide materials tend to react with H2O which adsorbed on their surface and thus deteriorate their structure and electrochemical performances. Accordingly, the air-sensitive sodium layered oxides should be well protected from the moist atmospheres, rendering a higher manufacturing and preservation cost. Here, based on the reaction mechanisms, critical influencing factors, and modification methods of layered oxides in moisture, we try to reach a comprehensive understanding of the air-stability of sodium layered oxides. Moreover, future efforts to resolve the air-stability of sodium layered oxides from Argonne National Laboratory will be also presented. References 1. Han, M. H.; Gonzalo, E.; Singh, G.; Rojo, T. A comprehensive review of sodium layered oxides: powerful cathodes for Na-ion batteries. Energy Environ. Sci. 2015, 8, 81-102. 2. Zuo, W.; Qiu, J.; Liu, X.; Ren, F.; Liu, H.; He, H.; Luo, C.; Li, J.; Ortiz, G. F.; Duan, H.; Liu, J.; Wang, M. S.; Li, Y.; Fu, R.; Yang, Y. The stability of P2-layered sodium transition metal oxides in ambient atmospheres. Commun. 2020, 11, 3544. 3. Xu, G. L.; Liu, X.; Zhou, X.; Zhao, C.; Hwang, I.; Daali, A.; Yang, Z.; Ren, Y.; Sun, C. J.; Chen, Z.; Liu, Y.; Amine, K. Native lattice strain induced structural earthquake in sodium layered oxide cathodes. Commun. 2022, 13, 436. 4. Zuo, W.; Xiao, Z.; Zarrabeitia, M.; Xue, X.; Yang, Y.; Passerini, S. Guidelines for Air-Stable Lithium/Sodium Layered Oxide Cathodes. ACS Materials Letters 2022, 4, 1074-1086. 5. Fu, F.; Liu, X.; Fu, X.; Chen, H.; Huang, L.; Fan, J.; Le, J.; Wang, Q.; Yang, W.; Ren, Y.; Amine, K.; Sun, S. G.; Xu, G. L. Entropy and crystal-facet modulation of P2-type layered cathodes for long-lasting sodium-based batteries. Commun. 2022, 13, 2826.
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Chiromawa, Idris Muhammad, Amiruddin Shaari, Razif Razali, Summanuwa Timothy Ahams i Mikailu Abdullahi. "Ab initio Investigation of the Structure and Electronic Properties of Normal Spinel Fe2SiO4". Malaysian Journal of Fundamental and Applied Sciences 17, nr 2 (29.04.2021): 195–201. http://dx.doi.org/10.11113/mjfas.v17n2.2018.
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Transition metal spinel oxides have recently been predicted to create efficient transparent conducting oxides for optoelectronic devices. These compounds can be easily tuned by doping or defect to adapt their electronic or magnetic properties. However, their cation distribution is very complex and band structures are still subject to controversy. We propose a complete density functional theory investigation of fayalite (Fe2SiO4) spinel, using Generalized Gradient Approximation (GGA) and Local Density Approximation (LDA) in order to explain the electronic and structural properties of this material. A detailed study of their crystal structure and electronic structure is given and compared with experimental data. The lattice parameters calculated are in agreement with the lattice obtained experimentally. The band structure of Fe2SiO4 spinel without Coulomb parameter U shows that the bands close to Fermi energy appear to be a band metal, with four iron d-bands crossing the Fermi level, in spite of the fact that from the experiment it is found to be an insulator.
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Nakhal, Suliman, i Martin Lerch. "New transition metal oxide fluorides with ReO3-type structure". Zeitschrift für Naturforschung B 71, nr 5 (1.05.2016): 457–61. http://dx.doi.org/10.1515/znb-2015-0215.
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AbstractThe new niobium oxide fluorides MNbO2F4 [M = (Cr, Fe)], CrNb2O4F5, and Fe2Nb3O6F9 were prepared by treatment of chromium or iron nitrate with Nb-containing hydrofluoric acid solutions. Crystal structures were investigated by means of X-ray powder diffraction. All new compounds can be structurally refined in the cubic ReO3-type. The iron niobium oxide fluorides are reddish orange, and chromium containing phases exhibit a light green color. The niobium atoms are in the highest formal oxidation state.
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Guo, Shaohua, Yang Sun, Jin Yi, Kai Zhu, Pan Liu, Yanbei Zhu, Guo-zhen Zhu, Mingwei Chen, Masayoshi Ishida i Haoshen Zhou. "Understanding sodium-ion diffusion in layered P2 and P3 oxides via experiments and first-principles calculations: a bridge between crystal structure and electrochemical performance". NPG Asia Materials 8, nr 4 (kwiecień 2016): e266-e266. http://dx.doi.org/10.1038/am.2016.53.
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Abstract Layered Na x MeO2 (Me=transition metal) oxides, the most common electrode materials for sodium-ion batteries, fall into different phases according to their stacking sequences. Although the crystalline phase is well known to largely influence the electrochemical performance of these materials, the structure–property relationship is still not fully experimentally and theoretically understood. Herein, a couple consisting of P2-Na0.62Ti0.37Cr0.63O2 and P3-Na0.63Ti0.37Cr0.63O2 materials having nearly the same compositions is reported. The atomic crystal structures and charge compensation mechanism are confirmed by atomic-scale characterizations in the layered P2 and P3 structures, respectively, and notably, the relationship of the crystal structure–electrochemical performance is well defined in the layered P-type structures for the first time in this paper. The electrochemical results suggest that the P2 phase exhibits a better rate capability and cycling stability than the P3 phase. Density functional theory calculations combined with a galvanostatic intermittent titration technique indicates that the P2 phase shows a lower Na diffusion barrier in the presence of multi-Na vacancies, accounting for the better rate capability of the P2 phase. Our results reveal the relationship between the crystal structure and the electrochemical properties in P-type layered sodium oxides, demonstrating the potential for future electrode advancements for applications in sodium-ion batteries.
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Maschmeyer, Elizabeth M., Liurukara D. Sanjeewa i Kulugammana G. S. Ranmohotti. "Crystal structure of BaMnB2O5containing structurally isolated manganese oxide sheets". Acta Crystallographica Section E Crystallographic Communications 72, nr 9 (19.08.2016): 1315–20. http://dx.doi.org/10.1107/s2056989016013074.
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In an attempt to search for mixed alkaline-earth and transition metal pyroborates, the title compound, barium manganese(II) pyroborate, has been synthesized by employing a flux method. The structure of BaMnB2O5is composed of MnO5square pyramids that form Mn2O8dimers by edge-sharing and of pyroborate units ([B2O5]4−) that are composed of two corner-sharing trigonal–planar BO3units. These building blocks share corners to form∞2[MnB2O5]2−layers extending parallel to (100). The Ba2+cations reside in the gap between two manganese pyroborate slabs with a coordination number of nine. The title compound forms an interesting spiral framework propagating along the 21screw axis. The structure is characterized by two alternating layers, which is relatively rare among known transition-metal-based pyroborate compounds.
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Brzezicki, Wojciech, Filomena Forte, Canio Noce, Mario Cuoco i Andrzej M. Oleś. "Tuning Crystal Field Potential by Orbital Dilution in Strongly Correlated d4 Oxides". Journal of Superconductivity and Novel Magnetism 33, nr 8 (30.12.2019): 2375–81. http://dx.doi.org/10.1007/s10948-019-05386-0.
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AbstractWe investigate the interplay between Coulomb-driven orbital order and octahedral distortions in strongly correlated Mott insulators due to orbital dilution, i.e., doping by metal ions without an orbital degree of freedom. In particular, we focus on layered transition metal oxides and study the effective spin–orbital exchange due to d3 substitution at d4 sites. The structure of the d3 − d4 spin–orbital coupling between the impurity and the host in the presence of octahedral rotations favors a distinct type of orbital polarization pointing towards the impurity and outside the impurity–host plane. This yields an effective lattice potential that generally competes with that associated with flat octahedra and, in turn, can drive an inversion of the crystal field interaction.
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Suturin, Sergey, Andrey Kaveev, Aleksandr Korovin, Vladimir Fedorov, Masahiro Sawada i Nikolai Sokolov. "Structural transformations and interfacial iron reduction in heterostructures with epitaxial layers of 3d metals and ferrimagnetic oxides". Journal of Applied Crystallography 51, nr 4 (5.07.2018): 1069–81. http://dx.doi.org/10.1107/s1600576718007823.
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The present paper sheds light on the interfacial structural transformation taking place upon epitaxial growth of ferromagnetic 3d metal compounds – Co, Ni and CoFeB – on the surface of magnetically ordered iron oxides – Fe3O4, Fe2O3 and Y3Fe5O12. The reducing conditions due to the excess of neutral metal atoms at the surface cause reduction of the Fe3+ ions of the underlying iron oxide layer to the Fe2+ state and subsequent recrystallization of the subsurface region to an MeO-like rock salt crystal structure. The corresponding change of the lattice symmetry can be readily recognized by in situ high-energy electron diffraction reciprocal-space mapping and ex situ X-ray diffraction techniques. From an analysis of diffraction and X-ray absorption data a tentative model of the structural transformation is proposed, based on penetration of Me atoms into the near-surface region of the iron oxide lattice. Once a few nanometre thick oxidized layer is formed, further growth of pure metallic film with native crystal structure takes place. An important observation made is that the oxidation/reduction effects do not occur when 3d metals are deposited onto more stable MgO and Gd3Ga5O12 surfaces. This circumstance makes it appropriate to propose these materials for use as buffer layers to prevent formation of antiferromagnetic monoxide transition regions in multilayered magnetic structures. The presented results are supposed valuable for development of hybrid ferromagnetic heterostructures attractive for various spintronic applications.
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Demazeau, Gérard, Samir F. Matar i Rainer Pöttgen. "Chemical Bonding in Metallic Rutile-type Oxides TO2 (T = Ru, Rh, Pd, Pt)". Zeitschrift für Naturforschung B 62, nr 7 (1.07.2007): 949–54. http://dx.doi.org/10.1515/znb-2007-0712.
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Abstract Synthesis routes to rutile-type oxides with 4d and 5d transition elements are summarized. Trends in electronic structure have been established through an analysis in the framework of density functional theory presenting the band structure, the density of states and the properties of chemical bonding. The metal-oxygen bond is found to play the major role in bonding of the system in the valence band. Throughout the series 4d → 5d (RuO2, RhO2, PdO2 and PtO2) the crystal field analysis of the band structure shows a lowering of eg towards t2g manifolds and a broadening of the overall density of states. In the vicinity of the Fermi level the role of the antibonding metal-oxygen character is investigated in the context of instability towards possible magnetic polarization, especially for RuO2.
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Lim, Jin-Myoung, Duho Kim, Min-Sik Park, Maenghyo Cho i Kyeongjae Cho. "Underlying mechanisms of the synergistic role of Li2MnO3 and LiNi1/3Co1/3Mn1/3O2 in high-Mn, Li-rich oxides". Physical Chemistry Chemical Physics 18, nr 16 (2016): 11411–21. http://dx.doi.org/10.1039/c6cp00088f.
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Synergistic roles of Li2MnO3 and NCM experimentally observed in high-Mn, Li-rich oxides were theoretically elucidated through the crystal field stabilisation of electronic structures, which reveals that NCM stabilises the transition metal layer of Li2MnO3.
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Kuklin, Mikhail S., i Antti J. Karttunen. "Crystal Structure Prediction of Magnetic Transition-Metal Oxides by Using Evolutionary Algorithm and Hybrid DFT Methods". Journal of Physical Chemistry C 122, nr 43 (11.10.2018): 24949–57. http://dx.doi.org/10.1021/acs.jpcc.8b08238.
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Spencer, Joseph A., Alyssa L. Mock, Alan G. Jacobs, Mathias Schubert, Yuhao Zhang i Marko J. Tadjer. "A review of band structure and material properties of transparent conducting and semiconducting oxides: Ga2O3, Al2O3, In2O3, ZnO, SnO2, CdO, NiO, CuO, and Sc2O3". Applied Physics Reviews 9, nr 1 (marzec 2022): 011315. http://dx.doi.org/10.1063/5.0078037.
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This Review highlights basic and transition metal conducting and semiconducting oxides. We discuss their material and electronic properties with an emphasis on the crystal, electronic, and band structures. The goal of this Review is to present a current compilation of material properties and to summarize possible uses and advantages in device applications. We discuss Ga2O3, Al2O3, In2O3, SnO2, ZnO, CdO, NiO, CuO, and Sc2O3. We outline the crystal structure of the oxides, and we present lattice parameters of the stable phases and a discussion of the metastable polymorphs. We highlight electrical properties such as bandgap energy, carrier mobility, effective carrier masses, dielectric constants, and electrical breakdown field. Based on literature availability, we review the temperature dependence of properties such as bandgap energy and carrier mobility among the oxides. Infrared and Raman modes are presented and discussed for each oxide providing insight into the phonon properties. The phonon properties also provide an explanation as to why some of the oxide parameters experience limitations due to phonon scattering such as carrier mobility. Thermal properties of interest include the coefficient of thermal expansion, Debye temperature, thermal diffusivity, specific heat, and thermal conductivity. Anisotropy is evident in the non-cubic oxides, and its impact on bandgap energy, carrier mobility, thermal conductivity, coefficient of thermal expansion, phonon modes, and carrier effective mass is discussed. Alloys, such as AlGaO, InGaO, (Al xIn yGa1− x− y)2O3, ZnGa2O4, ITO, and ScGaO, were included where relevant as they have the potential to allow for the improvement and alteration of certain properties. This Review provides a fundamental material perspective on the application space of semiconducting oxide-based devices in a variety of electronic and optoelectronic applications.
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Anguraj, G., R. Ashok Kumar, C. Inmozhi, R. Uthrakumar, Mohamed S. Elshikh, Saeedah Musaed Almutairi i K. Kaviyarasu. "MnO2 Doped with Ag Nanoparticles and Their Applications in Antimicrobial and Photocatalytic Reactions". Catalysts 13, nr 2 (12.02.2023): 397. http://dx.doi.org/10.3390/catal13020397.
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A wide range of nanoparticles have been produced for photocatalysis applications. Nonetheless, degrading organic dyes requires nanoparticles that are efficient and excellent. As a photocatalyst, pure manganese oxide (MnO2) was prepared via a sol–gel method using silver (Ag) nanoparticles of transition metal oxide. In addition to X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX), the crystal structure and elemental composition were analysed. According to XRD data, the transition metal of MnO2 oxide is highly pure and has a small crystallite size. The presence of functional groups was confirmed and clarified using Fourier-transform infrared spectra (FTIR). By irradiating the transition pure and doped MnO2 photocatalysts with visible light, the UV-vis, μ-Raman, and surface areas were determined. As a result, of using the photocatalysts with aqueous methylene blue (MB) solutions under visible light irradiation, the MnO2 doped with Ag nanoparticles demonstrated high degradation efficiencies and were utilised to establish heterogeneous photocatalysis dominance. In this paper, we demonstrate that the photocatalytic efficiency of transition metal oxides is exclusively determined by the particle size and surface area of nano-sized materials. Due to their high surface charge ratio and different surface orientations, have the highest photocatalytic efficiency. Generally, MnO2 doped with Ag nanoparticles is resistant to bacteria of both Gram-positive and Gram-negative types (B. sublittus and Escherichia coli). There is still a need for more research to be performed on reducing the toxicity of metal and metal oxide nanoparticles so that they can be used as an effective alternative to antibiotics and disinfectants, particularly for biomedical applications.
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Gourdon, O., V. Petricek i M. Evain. "A new structure type in the hexagonal perovskite family; structure determination of the modulated misfit compound Sr9/8TiS3". Acta Crystallographica Section B Structural Science 56, nr 3 (1.06.2000): 409–18. http://dx.doi.org/10.1107/s0108768100002160.
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Sr9/8TiS3, strontium titanium sulfide, a new phase in the hexagonal perovskite-like Sr x TiS3 system, has been prepared and its structure solved from single-crystal X-ray data within the (3 + 1)-dimensional [(3 + 1)D] formalism. Sr9/8TiS3 crystallizes with trigonal symmetry [R3¯m(00γ)0s superspace group], with the following lattice parameters: a s = 11.482 (3), c s = 2.9843 (8) Å, q = 0.56247 (7)c* and V s = 340.7 (3) Å3. The structure was considered as commensurate [R3¯c three-dimensional (3D) space group], but refined within the (3 + 1)D formalism to a residual factor R = 2.79% for 64 parameters and 1084 independent reflections. Original crenel functions were used for the sulfur and strontium description. The structure is different from that of the hexagonal perovskite-like oxide counterparts. The main difference is related to the presence of a new type of polyhedron in the [MS3] transition metal chains, intermediate between the octahedra classically found in such chains and the trigonal prismatic sites encountered in the oxides.
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Hoppe, Uwe. "Network-forming oxides with non-centrosymmetric structural groups – diffraction results on molybdate and tellurite glasses". Physics and Chemistry of Glasses: European Journal of Glass Science and Technology Part B 63, nr 6 (11.12.2022): 161–71. http://dx.doi.org/10.13036/17533562.63.6.13.
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The structural units of two types of conditional glass-forming oxides are irregular polyhedra whose distorted shapes result from intrinsic electronic causes. First example: The d0-transition metal cations Mo6+ form an amount of MoO6 in Ag molybdate glasses with the Mo6+ cation displaced towards an octahedral edge. Reverse Monte-Carlo results and comparisons with crystal structures corroborate the earlier diffraction interpretations of three distinct Mo−O distances in the MoO6 units. The post-transitional main group cation Te4+ forms high fractions of TeO5E units in phosphate glasses, where E denotes the lone-pair corner of the structural group. Instead of the regular TeO5E pyramids known for some related crystals, only irregular units are found in the glasses. The bond valences of their longest Te−O bonds are small, requiring the occurrence of three-fold coordinated oxygens.
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Zhang, Qin, Heng Chang Qian, Juan Pei i Suo Jia Yuan. "Competing Effects of Band Filling and Steric Factors on Magnetic and Transport Properties of Double Perovskite". Advanced Materials Research 490-495 (marzec 2012): 325–28. http://dx.doi.org/10.4028/www.scientific.net/amr.490-495.325.
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Ordered double perovskite oxides (Sr2-3xLa2xBax)FeMoO6 (0≤x≤0.3) have been investigated in this work. X-ray powder diffraction reveals that the crystal structure of the compounds changes from a tetragonal I4/m lattice to a cubic Fm m lattice around x=0.2. Due to the electron doping, the lattice constants increase with x. Owing to the competing contribution of electron doping and steric effect, Curie temperature of the compounds is almost unchanged. The resistivity of the parent compound shows a semiconducting behavior below room temperature, but those of the doped samples exhibit a metal-semiconductor transition. A correlation between the resistivity and metal-semiconducting transition temperature (TM-S) is observed. The resistivity and TM-S of the compounds decrease with x for x 0.2 and increase for x≥0.2.
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Pérez-Cruz, María Ana, María de la Paz Elizalde-González, Roberto Escudero, Sylvain Bernès, Rutilo Silva-González i Yasmi Reyes-Ortega. "At last! The single-crystal X-ray structure of a naturally occurring sample of the ilmenite-type oxide FeCrO3". Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 71, nr 5 (30.09.2015): 555–61. http://dx.doi.org/10.1107/s2052520615015838.
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A natural single crystal of the ferrimagnetic oxide FeCrO3, which was found in an opencast mine situated in the San Luis Potosí State in Mexico, has been characterized in order to elucidate some outstanding issues about the actual structure of this material. The single-crystal X-ray analysis unambiguously shows that transition metal cations are segregated in alternating layers normal to the threefold crystallographic axis, affording a structure isomorphous to that of ilmenite (FeTiO3), in the space group R \overline{3}. The possible occurrence of cation antisite and vacancy defects is below the limit of detection available from X-ray data. Structural and magnetic results are in agreement with the coherent slow intergrowth of magnetic phases provided by the two antiferromagnetic corundum-type parent oxides Fe2O3(hematite) and Cr2O3(eskolaite). Our results are consistent with the most recent density functional theory (DFT) studies carried out on digital FeCrO3[Sadat Nabi & Pentcheva (2011).Phys. Rev. B,83, 214424], and suggest that synthetic samples of FeCrO3might present a cation distribution different to that of the ilmenite structural type.
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Orii, Yuta, Masaki Kobayashi, Yuki Nagai, Kohei Atsumi, Daichi Tazaki, Satoshi Ehara i Takashiro Akitsu. "Anisotropic strain and Jahn-Teller effect of chiral complexes and metal oxides". Acta Crystallographica Section A Foundations and Advances 70, a1 (5.08.2014): C179. http://dx.doi.org/10.1107/s2053273314098209.
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For about a decade, we have systematically investigated thermally-accessible lattice strain and local pseudo Jahn-Teller distortion of [CuL2]3[M(CN)6]2·4H2O (L = (1R, 2R)-cyclohexanediamine; M = Cr, Co, and Fe). In mononuclear Cu(II) complexes, (pseudo) Jahn-Teller effect plays an important role in flexible distortion of crystal structures especially Cu(II) coordination environment. Beside Jahn-Teller distortion, we have dealt with some factors for example, metal substitution as bimetallic assemblies, chirality of ligands, and H/D isotope effect to vary intermolecular interaction and crystal packing. According to the course work using variable temperature PXRD, we have found that anisotropy of crystal strain distortion did not corporate with Jahn-Teller distortion around local coordination environment because of the discrepancy of the crystallographic axes and molecular alignment. In order to elucidate the anisotropic control of lattice strain and Jahn-Teller distortion closely, we have employed transition metal oxide with orthogonal or layered structures to prepare composite materials with the chiral metal complexes for discussion of thermally-accessible PXRD changes and IR shift due to adsorption. At first, we have employed chiral one-dimensional zig-zag Cu-Cr bimetallic assemblies and their oxides prepared by burining. Based on variable temperature XRD patterns, a linear correlation (lnK = a/T + b) of K (=d(T)-d(0)/d(T)) values, where d(T) and d(0) are spacing of lattice plane (d = nλ/(2sinθ)) at T K and 0 K (extrapolated), respectively, and its deviation from ideal correlation indicates degree of anisotropic lattice distortion of the composite materials. For example, we could observe LiMnO2, typical material of lithium ion battery, was enhanced anisotropic lattice strain along the b axis or the (011) plane added by [CuL2(H2O)2](NO3)2 complexes. Which may prevent from breaking down regular crystal structures during charge-discharge of secondary battery.
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Höwing, Jonas, Torbjörn Gustafsson i John O. Thomas. "Low-temperature structure of V6O13". Acta Crystallographica Section B Structural Science 59, nr 6 (25.11.2003): 747–52. http://dx.doi.org/10.1107/s0108768103023437.
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The structure of the transition metal oxide V6O13, a potential cathode material in lithium-polymer batteries, has been studied at 95 K using single-crystal X-ray diffraction (XRD). A phase transition has been determined by differential scanning calorimetry (DSC) measurements to occur at 153 K, with a heat of transition of −1.98 kJ mol−1. In this low-temperature phase, the V and O atoms move by up to 0.21 Å out of the mirror plane they occupy in the room-temperature structure. It is concluded that the earlier reported space group P21/a [Kawada et al. (1978). Acta Cryst. B34, 1037–1039] is incorrect and that a more appropriate choice of space group is Pc.
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Jin, Tao, i Rong Chang Zeng. "Structure and Infrared Radiation Properties of Metal Oxides-Doped Cordierites Using Graded Sintering Synthesis". Advanced Materials Research 311-313 (sierpień 2011): 140–44. http://dx.doi.org/10.4028/www.scientific.net/amr.311-313.140.
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The infrared radiation materials of transition metal oxides doped cordierite systems are synthesized using graded solid phase sintering. And the infrared radiation properties are investigated by means of X-ray diffraction, infrared spectrometry and scanning electron microscope. The results show that new compounds are developed during graded heat treatment from 900 °C to 1250 °C. The spinel phases produced are the main crystal material, and the different doped ions and impurity carbon cause the new phases, to different degree defect in this system ,which types can be classified into: (Mg,Zn,□)Fe2O4, (Mg,Zn,Co,□)Al2O4, (Co,□)Cr2O4,SiC etc., The main diffraction peaks of new phases formed are positioned at the zone (2θ) between 35.227o and 36.837o, and has stretching vibration peaks. And the main infrared absorption peaks located at the low wave number zone indicate to some degree deviation under different doped ions. The doped cordierites have infrared emissivity superior to that prepared with the conventional one-step synthesis. The full wave band integral emissivity of the spinel phases ranged between 0.88 and 0.94 at ambient temperature.
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Gagné, Olivier Charles, i Frank Christopher Hawthorne. "Bond-length distributions for ions bonded to oxygen: results for the transition metals and quantification of the factors underlying bond-length variation in inorganic solids". IUCrJ 7, nr 4 (9.06.2020): 581–629. http://dx.doi.org/10.1107/s2052252520005928.
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Bond-length distributions are examined for 63 transition metal ions bonded to O2− in 147 configurations, for 7522 coordination polyhedra and 41 488 bond distances, providing baseline statistical knowledge of bond lengths for transition metals bonded to O2−. A priori bond valences are calculated for 140 crystal structures containing 266 coordination polyhedra for 85 transition metal ion configurations with anomalous bond-length distributions. Two new indices, Δtopol and Δcryst, are proposed to quantify bond-length variation arising from bond-topological and crystallographic effects in extended solids. Bond-topological mechanisms of bond-length variation are (1) non-local bond-topological asymmetry and (2) multiple-bond formation; crystallographic mechanisms are (3) electronic effects (with an inherent focus on coupled electronic vibrational degeneracy in this work) and (4) crystal-structure effects. The indices Δtopol and Δcryst allow one to determine the primary cause(s) of bond-length variation for individual coordination polyhedra and ion configurations, quantify the distorting power of cations via electronic effects (by subtracting the bond-topological contribution to bond-length variation), set expectation limits regarding the extent to which functional properties linked to bond-length variation may be optimized in a given crystal structure (and inform how optimization may be achieved) and more. These indices further provide an equal footing for comparing bond-length variation and the distorting power of ions across ligand types, including resolution for heteroligand polyhedra. The observation of multiple bonds is found to be primarily driven by the bond-topological requirements of crystal structures in solids. However, sometimes multiple bonds are observed to form as a result of electronic effects (e.g. the pseudo Jahn–Teller effect, PJTE); resolution of the origins of multiple-bond formation follows calculation of the Δtopol and Δcryst indices on a structure-by-structure basis. Non-local bond-topological asymmetry is the most common cause of bond-length variation in transition metal oxides and oxysalts, followed closely by the PJTE. Non-local bond-topological asymmetry is further suggested to be the most widespread cause of bond-length variation in the solid state, with no a priori limitations with regard to ion identity. Overall, bond-length variations resulting from the PJTE are slightly larger than those resulting from non-local bond-topological asymmetry, comparable with those resulting from the strong JTE, and less than those induced by π-bond formation. From a comparison of a priori and observed bond valences for ∼150 coordination polyhedra in which the strong JTE or the PJTE is the main reason underlying bond-length variation, the JTE is found not to have a cooperative relation with the bond-topological requirements of crystal structures. The magnitude of bond-length variation caused by the PJTE decreases in the following order for octahedrally coordinated d 0 transition metal oxyanions: Os8+ > Mo6+ > W6+ >> V5+ > Nb5+ > Ti4+ > Ta5+ > Hf4+ > Zr4+ > Re7+ >> Y3+ > Sc3+. Such ranking varies by coordination number; for [4] it is Re7+ > Ti4+ > V5+ > W6+ > Mo6+ > Cr6+ > Os8+ >> Mn7+; for [5] it is Os8+ > Re7+ > Mo6+ > Ti4+ > W6+ > V5+ > Nb5+. It is concluded that non-octahedral coordinations of d 0 ion configurations are likely to occur with bond-length variations that are similar in magnitude to their octahedral counterparts. However, smaller bond-length variations are expected from the PJTE for non-d 0 transition metal oxyanions.
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Wach, Anna, Jacinto Sá i Jakub Szlachetko. "Comparative study of the around-Fermi electronic structure of 5d metals and metal-oxides by means of high-resolution X-ray emission and absorption spectroscopies". Journal of Synchrotron Radiation 27, nr 3 (14.04.2020): 689–94. http://dx.doi.org/10.1107/s1600577520003690.
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The composition of occupied and unoccupied electronic states in the vicinity of Fermi energies is vital for all materials and relates to their physical, chemical and mechanical properties. This work demonstrates how the combination of resonant and non-resonant X-ray emission spectroscopies supplemented with theoretical modelling allows for quantitative analysis of electronic states in 5d transition metal and metal-oxide materials. Application of X-rays provides element selectivity that, in combination with the penetrating properties of hard X-rays, allows determination of the composition of electronic states under working conditions, i.e. non-vacuum environment. Tungsten metal and tungsten oxide are evaluated to show the capability to simultaneously assess composition of around-band-gap electronic states as well as the character and magnitude of the crystal field splitting.
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Bachir Bouiadjra, Oussama, Ghouti Merad, Jean Marc Raulot, Hayet Si Abdelkader i Claude Esling. "Structural, Electronic and Mechanical Properties of Perovskite Oxides LaMO3 (M = Mn, Ni) Compounds in the High and Low Symmetric Phases by First Principle Calculation". Materials Science Forum 941 (grudzień 2018): 2300–2305. http://dx.doi.org/10.4028/www.scientific.net/msf.941.2300.
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The widely investigated perovskite oxides has attracted for a long time a great interest on the physical properties, in their bulk structures as well as the heterostructures components. The Lanthanum transition metal oxides LaMO3(M= Transition metal) is part of, due to their potential use in advanced technology (including superconductivity, magnetoresistance, ionic conductivity, and a multitude of dielectric properties). Despite the broad exploration of the physical properties, we found a considerable lack in the investigation of the mechanical properties of the LaMO3compounds. By applying the Density Functional Theory (DFT), we shed light on the structural, electronic, and especially mechanical properties of the experimentally verified phases of The LaMnO3, and LaNiO3. We first calculated the structural and electronic properties, then we continue with the single-crystal elastic constants and mechanical properties, where the bulk, shear and Young’s moduli, and the Anisotropy indexes were deduced, in order to remedy the existing gap of the theoretical knowledge about the mechanical behavior of the LaMnO3, and LaNiO3compounds.
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Ollivier, Patricia J., Jeffrey R. D. DeBoard, Pamela J. Zapf, Jon Zubieta, Linda M. Meyer, Chwan-Chin Wang, Thomas E. Mallouk i Robert C. Haushalter. "Hydrothermal synthesis and crystal structures of two novel vanadium oxides containing interlamellar transition metal complexes". Journal of Molecular Structure 470, nr 1-2 (październik 1998): 49–60. http://dx.doi.org/10.1016/s0022-2860(98)00469-4.
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Stegemann, Bert, Matthias Klemm, Siegfried Horn i Mathias Woydt. "Switching adhesion forces by crossing the metal–insulator transition in Magnéli-type vanadium oxide crystals". Beilstein Journal of Nanotechnology 2 (27.01.2011): 59–65. http://dx.doi.org/10.3762/bjnano.2.8.
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Magnéli-type vanadium oxides form the homologous series V n O2 n -1 and exhibit a temperature-induced, reversible metal–insulator first order phase transition (MIT). We studied the change of the adhesion force across the transition temperature between the cleavage planes of various vanadium oxide Magnéli phases (n = 3 … 7) and spherical titanium atomic force microscope (AFM) tips by systematic force–distance measurements with a variable-temperature AFM under ultrahigh vacuum conditions (UHV). The results show, for all investigated samples, that crossing the transition temperatures leads to a distinct change of the adhesion force. Low adhesion corresponds consistently to the metallic state. Accordingly, the ability to modify the electronic structure of the vanadium Magnéli phases while maintaining composition, stoichiometry and crystallographic integrity, allows for relating frictional and electronic material properties at the nano scale. This behavior makes the vanadium Magnéli phases interesting candidates for technology, e.g., as intelligent devices or coatings where switching of adhesion or friction is desired.
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Chando, Paul, Jacob Shellhamar, Elizabeth Wall i Ian Hosein. "Investigation of Transition Metal Oxide Post-Spinels for Calcium-Ion Batteries". ECS Meeting Abstracts MA2022-02, nr 4 (9.10.2022): 447. http://dx.doi.org/10.1149/ma2022-024447mtgabs.
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The dependence on lithium for rising global energy demand coupled with the scarcity of lithium necessitates the exploration of post-lithium strategies. Calcium-ion batteries are one such post-lithium strategy that can mitigate rising costs owing to calcium’s natural abundancy. A critical gap in this field is the lack of cathodes capable of intercalating calcium at high voltages and capacities while also retaining structural stability. The handful of candidates evaluated thus far have been plagued by low capacities and poor cycling performance due to intercalation–induced phase changes and instability. Transition metal oxide post–spinel–type materials have been identified as potential candidates for reversible Ca–ion storage owing to their crystal structures and high theoretical energy densities. However, experimental validation of these theoretical predictions remains largely unaddressed. In this work, post-spinel Calcium Iron Oxide (CaFe2O4) and Calcium Manganese Oxide (CaMn2O4) are explored as cathodes for calcium-ion batteries. The redox activity of each cathode is investigated using galvanostatic (GS) cycling while their structural stabilities are evaluated with X-ray diffraction (XRD) and scanning electron microscopy (SEM). The use of GS in tandem with XRD and SEM provides insights into the evolution of crystal structure with Ca–ion–transport within each cathode. Our results reveal that these post–spinel systems can cycle with a reversible capacity of 56 mAh/g, making them promising cathode candidates for Ca–ion batteries and warrant further investigation.
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Fung, Kuan-Zong, Shu-Yi Tsai i Jen-Hao Yang. "(Digital Presentation) Performance Improvement of Nickel-Rich Layered Cathodes for Li Batteries Based on Modified Solid State Reaction". ECS Meeting Abstracts MA2022-01, nr 6 (7.07.2022): 2500. http://dx.doi.org/10.1149/ma2022-0162500mtgabs.
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Lithiated metal oxides with layered structure used as the cathode may provide a high capacity and stable cycle retention, which is a desired property for lithium-ion batteries. Among them, NMC composed of Ni, Mn and Co as transition metal ions is considered a promising positive electrode. Due to high cost and toxicity of Co, Ni-rich layered oxide with substitution of Ni for Co content shows high capacity and adequate cycling performance. Recently, the fabrication of NMC adopting single-crystal (grain size: 1~6 μm) process tends to give better long-term performance than ones with particles in nanometer range. In this study, LiNi0.8Mn0.1Co0.1O2 (NMC811) with substitution of Ni/Mn for Co were selected as the Ni-rich layered cathode investigated. Due to the low melting point of Li2CO3, the heating temperature/time of powder mixture become crucial to control the adequate grain size of to achieve better retention. The value of the I(003) /I(104) ratio in XRD pattern represent cation mixing in layered structure. And this parameter is closely related to its electrochemical properties. Discussion will be carried out based on the results of XRD analysis and the charge–discharge profiles and cycling performance.
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Botton, Gianluigi, Matthieu Bugnet, Nicolas Gauquelin i Guo-zhen Zhu. "High-Resolution STEM and EELS as Tools to Study Structure and Bonding of Oxides". Acta Crystallographica Section A Foundations and Advances 70, a1 (5.08.2014): C1452. http://dx.doi.org/10.1107/s2053273314085477.
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Due to the developments of aberration correctors, bright electron sources, stable microscopes and electron monochromators, electron microscopy has dramatically evolved in the recent years. The current microscopes provide structural, chemical and spectroscopic information with sub-angstrom resolution and with synchrotron-quality spectroscopic performance ranging from the mid-infrared to the hard X-ray regime. Using a combination of scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) with better than 0.1eV energy resolution (down to 10meV), we provide here a review of recent studies where EELS and STEM have allowed us to probe the structure, the local chemistry and the nature of the local electronic structure of a range of complex oxides. These studies show that it is possible to determine the location of particular atomic species used as dopants in a crystal [1], the local coordination and valence of atoms in crystals and at surfaces [2,3], and also the nature of the hybridization and valence in perovskites [4] and superconductors [5,6]. These applications show that EELS and STEM can be used to resolve ambiguities in structure refinements of oxides by deducing the site preference of transition metal atoms and their coordination. We also show that it is possible to extract valence information and localization of electron charge in a range of materials, thus providing essential information on termination at interfaces [7]. With these techniques, we explore defects in materials and the nature of the electronic structure at interfaces.
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McCloy, John S., José Marcial, Deepak Patil, Muad Saleh, Mostafa Ahmadzadeh, Hua Chen, Jarrod V. Crum i in. "Glass structure and crystallization in boro-alumino-silicate glasses containing rare earth and transition metal cations: a US-UK collaborative program". MRS Advances 4, nr 17-18 (2019): 1029–43. http://dx.doi.org/10.1557/adv.2019.99.
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ABSTRACTNuclear wastes generated from reprocessing of used nuclear fuel tend to contain a large fraction of rare earth (RE, e.g., Nd3+), transition (TM, e.g., Mo6+, Zr4+), alkali (A, e.g., Cs+), and alkaline earth cations (AE, e.g., Ba2+, Sr2+). Various strategies have been considered for immobilizing such waste streams, varying from nominally crystal-free glass to glass-ceramic to multi-phase ceramic waste forms. For glass and glass-ceramic waste forms, the added glass-forming system is generally alkali-alkaline earth-aluminoborosilicate (i.e., Na-Ca-Al-B-Si oxide). In a US-UK collaborative project, summarized here, we investigated the glass structure and crystallization dependence on compositional changes in simulated nuclear waste glasses and glass-ceramics. Compositions ranged in complexity from five – to – eight oxides. Specifically, the roles of Mo and rare earths are investigated, since a proposed glass-ceramic waste form contains crystalline phases such as powellite [(AE,A,RE)MoO4] and oxyapatite [(RE,AE,A)10Si6O26], and the precipitation of molybdenum phases is known to be affected by the rare earth concentration in the glass. Additionally, the effects of other chemical additions have been systematically investigated, including Zr, Ru, P, and Ti. A series of studies were also undertaken to ascertain the effect of the RE size on glass structure and on partitioning to crystal phases, investigating similarities and differences in glasses containing single RE oxides of Sc, Y, La, Ce, Nd, Sm, Er, Yb, or Lu. Finally, the effect of charge compensation was investigated by considering not only the commonly assessed peralkaline glass but also metaluminous and peraluminous compositions. Glass structure and crystallization studies were conducted by spectroscopic methods (i.e., Raman, X-ray absorption, nuclear magnetic resonance (NMR), optical absorption, photoluminescence, photoluminescence excitation, X-ray photoelectron spectroscopy), microscopy (i.e., scanning electron microscopy, transmission electron microscopy, electron probe microanalysis), scattering (i.e., X-ray and neutron diffraction, small angle measurements), and physical characterization (i.e., differential thermal analysis, liquidus, viscosity, density). This paper will give an overview of the research program and some example unpublished results on glass-ceramic crystallization kinetics, microstructure, and Raman spectra, as well as some examples of the effects of rare earths on the absorption, luminescence, and NMR spectra of starting glasses. The formal collaboration described here has resulted in the generation of a large number of results, some of which are still in the process of being published as separate studies.
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Gudat, Axel, Sabine Haag, Rüdiger Kniep i Albrecht Rabenau. "Ternäre Nitride des Lithiums mit den Elementen Cr, Mo und W / Ternary Lithium Nitrides with Elements Cr, Mo and W". Zeitschrift für Naturforschung B 45, nr 2 (1.02.1990): 111–20. http://dx.doi.org/10.1515/znb-1990-0203.
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The ternary compounds were prepared by reaction of the transition metals with Li3N melt under nitrogen. The crystal structures of Li6MeN4 (P42/nmc, Z = 2; Me = Mo: a = 667.3(1) pm, c = 492.5(3) pm; Me = W: a = 667.9(1) pm, c = 492.7(1) pm) and Li15Cr2N9 (P4/ncc, Z = 4; a = 1023.3(5) pm, c = 938.9(7) pm) can be described as fluorite-type superstructures with the lithium and transition metal atoms in tetrahedral holes of the nearly fcc nitrogen arrangement and with an ordered distribution of defects within the cation substructure. In addition, the ternary system Li–Cr–N contains the compound Li6CrN4 with a crystal structure which is not quite clear at present, but which shows close relations to the structures of Li6MeN4 (Me = Mo, W). The previously reported compounds Li9MeN5 (Me = Cr, Mo, W) have not been observed during this study. The respective Cr compound in fact is a nitride-oxide (nitride-imide) of composition Li14Cr2N8(O,NH) with a crystal structure (P3̄, Z = 1, a = 579.9(1) pm, c = 826.3(6) pm) also showing a fluorite-type superstructure.
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Ben Yahia, Hamdi, Antoine Villesuzanne, Ute Ch Rodewald, Thomas Schleid i Rainer Pöttgen. "Condensed [OPr4]10+ and Discrete [AsO3]3–Ψ1-Tetrahedra in Pr5O4Cl[AsO3]2". Zeitschrift für Naturforschung B 65, nr 5 (1.05.2010): 549–55. http://dx.doi.org/10.1515/znb-2010-0503.
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The oxide chloride arsenite Pr5O4Cl[AsO3]2 was obtained as green crystals as a by-product of the synthesis of PrOTAs oxide arsenides (T = late transition metal), starting from Pr6O11, a transition metal oxide, arsenic, and an NaCl/KCl flux. Pr5O4Cl[AsO3]2 crystallizes with the monoclinic Nd5O4Cl[AsO3]2-type structure, space group C2/m. The structure was refined from single-crystal diffractometer data: a = 12.4943(15), b = 5.6884(13) c = 9.0776(19) Å , β = 116.61(1)°, R(F) = 0.0264, wR(F2) = 0.0509, 542 F2 values, and 52 variables. It is built up from corrugated layers of edge- and corner-sharing [OPr4]10+ tetrahedra, which are connected via chloride anions. The space between the layers is filled by these Cl− and discrete arsenite anions [AsO3]3− with lone pairs pointing towards each other. The network of condensed [OPr4]10+ tetrahedra is compared with the different arrays in the oxide pnictides α-PrOZnP, and in β -PrOZnP. Arsenic lone pair energy bands, main interactions, and the spatial distribution were identified precisely using density functional theory (DFT). Among the three crystallographically different sites for praseodymium, one was found non-magnetic in these calculations.
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Chai, Lili, Huizi Ye, Zhengguang Hu, Fengliang Liu, Liyun Qin, Zhiqi Zhang, Xianxin Lai, Yong Zhao i Li Wang. "Tuning the Architecture of Hierarchical Porous CoNiO2 Nanosheet for Enhanced Performance of Li-S Batteries". Batteries 8, nr 12 (29.11.2022): 262. http://dx.doi.org/10.3390/batteries8120262.
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As the desired components and crystal structure of a transition metal oxide catalyst are selected, architecture is a dominating factor affecting its electrocatalytic performance for applications in lithium-sulfur (Li-S) batteries. Nano-compounds with a hollow architecture are undoubtedly the ideal catalysts for enhancing cathodic performance for more exposed active sites and shortened path lengths than are other architectures. Additionally, the internal stress in hollow architecture is favorable for further performance enhancement, due to its regulation effects of driving the d-band center of the transition metal in the active sites to migrate toward the Fermi level, which will promote the chemical adsorption and catalytic conversion of the polysulfides (PSs). To this point, we select hierarchical porous dual transition metal oxide CoNiO2 nano-boxes (CoNiO2(B)) as the conceptual model; meanwhile, CoNiO2 nano-flakes (CoNiO2(F)) with identical stoichiometry and crystal structure are also analyzed as a comparison. Li-S batteries based on CoNiO2(B) deliver superior energy storage features, including a reversible discharge capacity of 1232 mAh g−1 at 0.05 C and a stable cycle performance with decay rate of 0.1% each cycle even after 300 cycles at 1 C. This research presents an alternative scheme for booting the performance of Li-S batteries.
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Banik, Trapa, i Indranil Bhattacharya. "Potency of Potassium Doping on Na-Ion Sites to Avert Phase Transition in P2 Type Sodium-Ion Battery". ECS Meeting Abstracts MA2022-02, nr 4 (9.10.2022): 415. http://dx.doi.org/10.1149/ma2022-024415mtgabs.
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Sodium-ion battery (SIB) is acquiring considerable attention as a viable replacement to lithium-ion battery (LIB) technology in the ever-expanding energy storage market due to its attractive combination of homogeneous profusion in the earth and identical intercalation chemistry to LIB. However, SIB is still a laboratory child as SIBs exhibit slightly lower energy density as compared to those of LIBs. Hence, it is critical to determine a suitable cathode to facilitate facile Na-ion transport as cathode is the key factor affecting cycle life, energy density as well as safety. In case of SIBs, layered transition metal oxides are widely preferred as cathode material due to their excellent high specific capacity as well as their simple synthesis process. In this research, Manganese enriched P2 type quaternary Na0.6Fe0.48Mn0.5Ti0.01V0.01O2 (NFMTV) cathode material is studied which shows high capacity and high voltage (4.2V) along with reducing Jahn-Teller (JT) Effect. However, inferior reversibility and capacity fading have still been a challenge, particularly for higher voltage window as lower Na content during discharge process initiates the unavoidable phase transition. To preserve the lattice orientation, a feasible approach is demonstrated in this research by introducing potassium (K) ion into Na ion sites between transition metal oxide (TMO2) layers. This work explains that the K+ into Na+ ion layers serve as the supporting pillar to hold the stacking pattern intact even for very low Na content at higher voltage. As seen from the SEM and EDS analysis, no apparent alternation happened in surface morphology and crystal structure for a small amount of K doping. Furthermore, the XRD and Rietveld refinement results validate that emplacement of K+ ions in the Na sites in the NFMTV crystal structure. It also expands the Na+ ion diffusion path and substantially boosts the rate performance and reversibility. Besides, K+ ion doping halts the gliding phenomenon and hence, phase transition is impeded which is observed from the improved cyclability and capacity retention.
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Rana, Supriya, Krishna Kumar Yadav, Surinder Kumar Mehta i Menaka Jha. "Oxalate Assisted Growth of Hybrid Nickel Cobalt-Based Nanostructures for Hydrogen Generation Via Urea Oxidation". ECS Meeting Abstracts MA2022-01, nr 47 (7.07.2022): 1981. http://dx.doi.org/10.1149/ma2022-01471981mtgabs.
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Hybrid mixed transition metal oxides nanostructures as spinal act as promising electrode materials for energy-related applications. In the present work, a design and synthesis of mixed metal oxide nanostructures have been done by increasing the nickel content in the crystal structure of Co3O4 spinel by using template-assisted oxalate route via conzventional coprecipitation method for syntheses. Selectively controlling the Ni: Co ratio will result in a significant change in the morphology of the nanostructures. Further, kinetically controlled thermal decomposition of nickel and cobalt oxalate precursors results in the formation of anisotropically aligned ultrafine nanoparticle self-assembly to form nanocubes and nanorods. Whereas the mixture of nickel-cobalt oxalate precursor after decomposition led to the formation of nanoparticles assembly that is interconnected and hierarchically arranged to form nanosheets that align themselves in a particular orientation to give a three-dimensional micro flower structure. This hybrid structure with increased porosity and higher exposed active sites acts as an efficient electrocatalyst to promote water and urea oxidation in alkaline media. The hybrid catalyst shows overpotential of 300 mV and -190 mV towards water oxidation in alkaline media with excellent stability for 24 h. Similarly, during urea oxidation, the significant loss in the potential to 1.31 V can be seen to achieve the current density of 10 mA/cm2 compared to the potential required in urea-free electrolysis. So, this work provides better insights for tuning snd designing the hybrid structures and regulating their morphological characteristics for enhanced catalytic performance.
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Förster, Stefan, Eva Zollner, Klaus Meinel, Renè Hammer, Martin Trautmann i Wolf Widdra. "2D quasicrystals from perovskites". Acta Crystallographica Section A Foundations and Advances 70, a1 (5.08.2014): C80. http://dx.doi.org/10.1107/s2053273314099197.
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Perovskite oxides represent a versatile class of materials with a simple cubic or pseudo-cubic crystal structure. The family of perovskite oxides contains insulators, metals, semiconductors, and superconductors with nearly identical lattice parameters. This structural equivalence additionally allows to combine perovskites with different properties in multilayer systems to produce functional materials with unique properties. We report here on the formation of a quasicrystal (QC) thin film on a threefold Pt(111) surface. This QC film is derived from the classical perovskite oxide BaTiO3 which is the most intensely studied ferroelectric perovskite oxide. An easily accessible ferroelectric to paraelectric phase transition at 400 K makes the material so interesting for basic and applied research. Due to matching lattice conditions BaTiO3 can be grown epitaxially on selected metal substrates. Periodic thin films of either BaTiO3(100) or BaTiO3(111) have been grown depending on substrate orientation and preparation conditions on Pt(001) and on Pt(111) [1, 2]. As we demonstrate here, astonishingly also a two-dimensional dodecagonal quasicrystalline structure can be formed by annealing an initially 1.4 nm thick BaTiO3 film on Pt(111) [3]. It develops at a temperature of 1250 K from a wetting layer spreading between a few thicker BaTiO3(111) islands. Surface sensitive electron diffraction (LEED) shows a bright and sharp pattern with dodecagonal symmetry. High-resolution scanning tunneling microscopy (STM) images reveal an arrangement of quadratic, triangular, and rhombic elements which compares well to a Gähler tiling. The development of higher-order self-similar structures is widely suppressed by a linear phason strain. This is supported by the fine structure of the diffraction data.
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Georgescu, Alexandru B., Oleg E. Peil, Ankit S. Disa, Antoine Georges i Andrew J. Millis. "Disentangling lattice and electronic contributions to the metal–insulator transition from bulk vs. layer confined RNiO3". Proceedings of the National Academy of Sciences 116, nr 29 (2.07.2019): 14434–39. http://dx.doi.org/10.1073/pnas.1818728116.
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In complex oxide materials, changes in electronic properties are often associated with changes in crystal structure, raising the question of the relative roles of the electronic and lattice effects in driving the metal–insulator transition. This paper presents a combined theoretical and experimental analysis of the dependence of the metal–insulator transition of NdNiO3 on crystal structure, specifically comparing properties of bulk materials to 1- and 2-layer samples of NdNiO3 grown between multiple electronically inert NdAlO3 counterlayers in a superlattice. The comparison amplifies and validates a theoretical approach developed in previous papers and disentangles the electronic and lattice contributions, through an independent variation of each. In bulk NdNiO3, the correlations are not strong enough to drive a metal–insulator transition by themselves: A lattice distortion is required. Ultrathin films exhibit 2 additional electronic effects and 1 lattice-related effect. The electronic effects are quantum confinement, leading to dimensional reduction of the electronic Hamiltonian and an increase in electronic bandwidth due to counterlayer-induced bond-angle changes. We find that the confinement effect is much more important. The lattice effect is an increase in stiffness due to the cost of propagation of the lattice disproportionation into the confining material.
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Li, Mengjie, Jie Dong, Dongmei Deng, Xun Ouyang, Xiaoxia Yan, Shima Liu i Liqiang Luo. "Mn3O4/NiO Nanoparticles Decorated on Carbon Nanofibers as an Enzyme-Free Electrochemical Sensor for Glucose Detection". Biosensors 13, nr 2 (13.02.2023): 264. http://dx.doi.org/10.3390/bios13020264.
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Transition metal oxides have garnered a lot of attention in the field of electrocatalysis along with their unique crystal structure and excellent catalytic properties. In this study, carbon nanofibers (CNFs) decorated with Mn3O4/NiO nanoparticles were made using electrospinning and calcination. The conductive network constructed by CNFs not only facilitates electron transport, but also provides landing sites for nanoparticles, thus reducing nanoparticle aggregation and exposing more active sites. Additionally, the synergistic interaction between Mn3O4 and NiO improved electrocatalytic capacity for glucose oxidation. The Mn3O4/NiO/CNFs modified glassy carbon electrode shows satisfactory results in terms of linear range and anti-interference capability for glucose detection, suggesting that the constructed enzyme-free sensor has a promising application in clinical diagnosis.
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Hartwig, Sabina, i Harald Hillebrecht. "The Crystal Structure of NbO2I – A Double-layer Structure with 7-Coordinated Niobium". Zeitschrift für Naturforschung B 62, nr 12 (1.12.2007): 1543–48. http://dx.doi.org/10.1515/znb-2007-1212.
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Single crystals of NbO2I were obtained as dark red needles by chemical transport. According to the structure determination (Pnma, a = 20.897(4), b = 3.7654(8), c = 3.9715(8) Å , Z = 4, 619 reflections, 26 variables, R1(F) = 0.0645, wR2(F2) = 0.1597) NbO2I represents a new structure type with 7- coordinated Nb atoms. Pentagonal bipyramids NbO5I2 are connected via the apical O atoms with alternating short and long Nb-O distances (1.79 / 2.20 Å ) to chains and via the three equatorial O atoms to double layers. Between the double layers there are only weak van-der-Waals interactions of the I atoms. NbO2I is the first oxide halide of a transition metal with CN 7. Structurally NbO2I is closely related to UO2Br, but with alternating short and long Nb-O distances as a difference.