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A. Yu. Zuev - One of the best experts on this subject based on the ideXlab platform.
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Defect Structure and related properties of mayenite Ca12Al14O33
Solid State Ionics, 2015Co-Authors: Dmitry S. Tsvetkov, A.s. Steparuk, A. Yu. ZuevAbstract:Abstract For the first time, the Defect Structure of mayenite was developed on the basis of conventional Kroger–Vink method and successfully verified using available data on its properties such as total conductivity, hydration/dehydration and oxidation/reduction. As a consequence, equilibrium constants of the quasichemical reactions of mayenite reduction and hydration were determined as a function of temperature. This allowed estimation of Ca 12 Al 14 O 33 − δ enthalpy of reduction and hydration. The former was found to be equal to 360 kJ/mol while the latter was estimated as − 238 kJ/mol. The Defect Structure model proposed enabled estimation of oxygen nonstoichiometry in mayenite.
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Defect Structure and Defect-Induced Expansion of MIEC Oxides: Doped Lanthanum Cobaltites
Journal of The Electrochemical Society, 2012Co-Authors: A. Yu. Zuev, Vladimir V. Sereda, Dmitry S. TsvetkovAbstract:Perovskites based upon substituted LaCoO3-δ are the state-of-the-art materials for a variety of different devices for moderate high temperature applications such as solid oxide fuel cells (SOFCs) and mixed ionic and electronic conducting (MIEC) membranes. The unique feature of the oxides is their ability to undergo both thermal expansion and that induced by the Defects of oxygen nonstoichiometry in the oxide lattice. The latter is chemical or Defect-induced expansion. This property is extremely sensitive to the Defect Structure of the oxide material. Therefore reliable data on the Defect Structure of oxide materials is of key importance to understanding the origin of their chemically induced lattice strain. On the other hand, chemical expansion of oxide crystal cell precisely measured with ppm-resolution allows better understanding its local electronic and Defect Structure. © 2012 The Electrochemical Society. All right reserved
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Oxygen nonstoichiometry and Defect Structure of undoped and doped lanthanum cobaltites
Journal of Materials Science, 2007Co-Authors: A. Yu. Zuev, A. N. Petrov, A. I. Vylkov, D. S. TsvetkovAbstract:The results of oxygen nonstoichiometry are presented for the perovskite-type undoped cobaltite LaCoO3-δ, doped with strontium La0.7Sr0.3CoO3-δ, and doped with copper LaCo0.7Cu0.3O3-δ as a function of oxygen partial pressure \({p_{\rm {O_2}}}\) and temperature. The modeling of the Defect Structure of these oxygen deficient perovskites is carried out. Two different Defect Structure models are evolved. Within the framework of the first model electrons are treated as quasi-free in LaCoO3-δ, partly trapped in La0.7Sr0.3CoO3-δ and LaCo0.7Cu0.3O3-δ, whereas holes are assumed to be itinerant in all oxides studied. The intrinsic electronic disordering process is taken into account as well. According to the second model electrons and holes are assumed to be localized. Thermal excited charge disproportionation of cobalt is considered as well. The corresponding equations for the law of mass action, electroneutrality condition, and mass balance give a set of nonlinear equations in the both cases. The analytical solutions of these sets yield general expressions which are used for the verification of the Defect models proposed by nonlinear curve fitting. The latter showed that both models of the Defect Structure of all lanthanum cobaltites studied fit the experimental data about equally good. It is, therefore, difficult to rule out either of Defect Structure models on the basis of equilibrium data on oxygen nonstoichiometry solely.
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Thermodynamics, Defect Structure, and charge transfer in doped lanthanum cobaltites: an overview
Journal of Solid State Electrochemistry, 2006Co-Authors: A. N. Petrov, V. A. Cherepanov, A. Yu. ZuevAbstract:This work, based on the experimental and theoretical research performed by the authors during last three decades, presents an overview of phase and Defect thermodynamics, electronic transport properties, and the stability of cobaltite-based mixed conductors that are promising for electrode and membrane applications. Attention is centered on (1) the phase equilibria in La–Me–Co–T–O (where Me=Ca, Sr, Ba and T=Mn, Fe, Ni, Cu) systems and crystal Structure of the complex oxides formed in these systems, thermodynamic stability and the homogeneity ranges of solid solutions; (2) the Defect Structure of the oxygen-deficient undoped and acceptor- or/and donor-doped lanthanum cobaltites; and (3) their conductivity and Seebeck coefficient as functions of temperature and oxygen partial pressure. The relationships between the peculiarities of the Defect Structure and the transport properties of the lanthanum cobaltites with different dopant natures are analyzed.
J D Jorgensen - One of the best experts on this subject based on the ideXlab platform.
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Defect Structure studies of bulk and nano indium tin oxide
Journal of Applied Physics, 2004Co-Authors: G B Gonzalez, Donald E Ellis, Thomas O Mason, J P Quintana, Oliver Warschkow, J H Hwang, J P Hodges, J D JorgensenAbstract:The Defect Structure of bulk and nano-indium-tin oxide was investigated by a combination of experimental techniques, including high-resolution synchrotron x-ray diffraction, extended x-ray absorption fine Structure, and time-of-flight neutron diffraction on powder specimens. The structural results include atomic positions, cation distributions, and oxygen interstitial populations for oxidized and reduced materials. These structural parameters were correlated with theoretical calculations and in situ electrical conductivity and thermopower measurements as well as existing Defect models, with special reference to the model of Frank and Kostlin [G. Frank and H. Kostlin, Appl. Phys. A 27, 197 (1982)].
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neutron diffraction study on the Defect Structure of indium tin oxide
Journal of Applied Physics, 2001Co-Authors: G B Gonzalez, J. B. Cohen, Thomas O Mason, J H Hwang, J P Hodges, J D JorgensenAbstract:The Defect Structure of undoped and Sn-doped In2O3 (ITO) materials was studied by preparing powders under different processing environments and performing neutron powder diffraction. The effect of tin doping and oxygen partial pressure was determined. Structural information was obtained by analyzing neutron powder diffraction data using the Rietveld method. The results include positions of the atoms, their thermal displacements, the fractional occupancy of the interstitial oxygen site, and the fractional occupancies of Sn on each of the two nonequivalent cation sites. The tin cations show a strong preference for the b site versus the d site. The measured electrical properties are correlated with the interstitial oxygen populations, which agree with the proposed models for reducible (2SnIn•Oi″)x and nonreducible (2SnIn•3OOOi″)x Defect clusters.
Th. Proffen - One of the best experts on this subject based on the ideXlab platform.
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discus a program for diffuse scattering and Defect Structure simulation
Journal of Applied Crystallography, 1997Co-Authors: Th. Proffen, Reinhard B. NederAbstract:The program DISCUS is a versatile tool for the analysis of diffuse scattering and for Defect Structure simulations. The model Structure can be created from an asymmetric unit of a unit cell or a complete Structure can be read from a file. A Fortran77 style interpreter that includes IF statements and various loops combined with predefined Defect types like thermal displacements, waves and microdomains allows one to create all sorts of Defect Structures. The Fourier-transform segment of the program allows one to calculate neutron as well as X-ray intensities including isotropic temperature factors and anomalous scattering. The calculation of the inverse and difference Fourier transform as well as the Patterson function is also implemented. A model Structure can be `fitted' to observed diffuse scattering data by reverse Monte Carlo (RMC) simulations. The RMC segment allows one to model displacive as well as occupational disorder. The program is completely written in Fortran77 and the source code is available via the World Wide Web.
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Defect Structure and diffuse scattering of zirconia single crystals doped with 7 mol% CaO
Acta Crystallographica Section B Structural Science, 1993Co-Authors: Th. Proffen, Reinhard B. Neder, Friedrich Frey, W. AssmusAbstract:The Defect Structure of 7 mol% calcium-stabilized zirconia (CSZ) is described in terms of a correlated distribution of microdomains within the cubic matrix of CSZ. It is shown that the Defect Structure is very similar to that of 15 mol% CSZ. The Defect Structure consists of two types of Defects: microdomains based on a single oxygen vacancy with relaxed neighbouring ions and microdomains based on a pair of oxygen vacancies separated by a3~/2/2 along (111). Calculations show that a tetragonal distortion cannot explain the observed diffuse scattering. Several arguments suggest that the Defect Structure is not that of the qO t phase: first, the similarity of diffuse scattering of yttrium-stabilized zirconia, for which no ~ phase exists; second, the diffuse scattering of CSZ is almost identical from 4 mol% CSZ up to 20 mol% CSZ; third, the diffuse scattering is temperature dependent; and fourth, a direct comparison of single-crystal intensities of the qo~ phase with the intensity of diffuse scattering.
G B Gonzalez - One of the best experts on this subject based on the ideXlab platform.
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Defect Structure studies of bulk and nano indium tin oxide
Journal of Applied Physics, 2004Co-Authors: G B Gonzalez, Donald E Ellis, Thomas O Mason, J P Quintana, Oliver Warschkow, J H Hwang, J P Hodges, J D JorgensenAbstract:The Defect Structure of bulk and nano-indium-tin oxide was investigated by a combination of experimental techniques, including high-resolution synchrotron x-ray diffraction, extended x-ray absorption fine Structure, and time-of-flight neutron diffraction on powder specimens. The structural results include atomic positions, cation distributions, and oxygen interstitial populations for oxidized and reduced materials. These structural parameters were correlated with theoretical calculations and in situ electrical conductivity and thermopower measurements as well as existing Defect models, with special reference to the model of Frank and Kostlin [G. Frank and H. Kostlin, Appl. Phys. A 27, 197 (1982)].
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neutron diffraction study on the Defect Structure of indium tin oxide
Journal of Applied Physics, 2001Co-Authors: G B Gonzalez, J. B. Cohen, Thomas O Mason, J H Hwang, J P Hodges, J D JorgensenAbstract:The Defect Structure of undoped and Sn-doped In2O3 (ITO) materials was studied by preparing powders under different processing environments and performing neutron powder diffraction. The effect of tin doping and oxygen partial pressure was determined. Structural information was obtained by analyzing neutron powder diffraction data using the Rietveld method. The results include positions of the atoms, their thermal displacements, the fractional occupancy of the interstitial oxygen site, and the fractional occupancies of Sn on each of the two nonequivalent cation sites. The tin cations show a strong preference for the b site versus the d site. The measured electrical properties are correlated with the interstitial oxygen populations, which agree with the proposed models for reducible (2SnIn•Oi″)x and nonreducible (2SnIn•3OOOi″)x Defect clusters.
W. Assmus - One of the best experts on this subject based on the ideXlab platform.
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Defect Structure and diffuse scattering of zirconia single crystals doped with 7 mol% CaO
Acta Crystallographica Section B Structural Science, 1993Co-Authors: Th. Proffen, Reinhard B. Neder, Friedrich Frey, W. AssmusAbstract:The Defect Structure of 7 mol% calcium-stabilized zirconia (CSZ) is described in terms of a correlated distribution of microdomains within the cubic matrix of CSZ. It is shown that the Defect Structure is very similar to that of 15 mol% CSZ. The Defect Structure consists of two types of Defects: microdomains based on a single oxygen vacancy with relaxed neighbouring ions and microdomains based on a pair of oxygen vacancies separated by a3~/2/2 along (111). Calculations show that a tetragonal distortion cannot explain the observed diffuse scattering. Several arguments suggest that the Defect Structure is not that of the qO t phase: first, the similarity of diffuse scattering of yttrium-stabilized zirconia, for which no ~ phase exists; second, the diffuse scattering of CSZ is almost identical from 4 mol% CSZ up to 20 mol% CSZ; third, the diffuse scattering is temperature dependent; and fourth, a direct comparison of single-crystal intensities of the qo~ phase with the intensity of diffuse scattering.
