Центральная Научная Библиотека УрО РАН

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   H 65


    High-temperature electrical conductivity and thermopower in nonstoichiometric La1-xSrxCoO3-delta (x = 0.6) [] / E. B. Mitberg, M. V. Patrakeev, I. A. Leonidov, V. L. Kozhevnikov, K. R. Poeppelmeier // Solid State Ionics. - 2000. - V. 130, N 3-4. - С. 325-330. - Библиогр.: 18 назв. . - ISSN 0167-2738

ББК 54
Рубрики: ХИМИЧЕСКИЕ НАУКИ
Кл.слова (ненормированные):
ЭЛЕКТРОПРОВОДНОСТЬ ВЫСОКОТЕМПЕРАТУРНАЯ -- ВЫСОКОТЕМПЕРАТУРНАЯ ЭЛЕКТРОПРОВОДНОСТЬ -- НЕСТЕХИОМЕТРИЯ -- ТЕРМОЭДС -- ЛАНТАН -- СТРОНЦИЙ -- КОБАЛЬТ -- ПРОВОДНИКИ СМЕШАННЫЕ -- СМЕШАННЫЕ ПРОВОДНИКИ -- КОБАЛЬТИТЫ -- ПРОВОДИМОСТЬ ЭЛЕКТРОННАЯ -- ЭЛЕКТРОННАЯ ПРОВОДИМОСТЬ -- La -- Sr -- Co

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   P 45


    Perovskite-like system (Sr, La)(Fe, Ga)O3-delta: structure and ionic transport under oxidizing conditions [] / V. V. Kharton, A. L. Shaulo, A. P. Viskup, M. Avdeev, A. A. Yaremchenko, M. V. Patrakeev, A. I. Kurbakov, E. N. Naumovich, F. M. B. Marques // Solid State Ionics. - 2002. - V. 150, N 3-4. - С. 229-243. - Bibliogr.: p. 243 (50 ref.) . - ISSN 0167-2738

ББК 54
Рубрики: ХИМИЧЕСКИЕ НАУКИ
Кл.слова (ненормированные):
ПЕРОВСКИТЫ -- СМЕШАННЫЕ ПРОВОДНИКИ -- ПРОВОДНИКИ СМЕШАННЫЕ -- ОКИСЛЕНИЕ -- ИОННАЯ ПРОВОДИМОСТЬ -- ПРОВОДИМОСТЬ ИОННАЯ -- КРИСТАЛЛИЧЕСКАЯ СТРУКТУРА -- СТРУКТУРА КРИСТАЛЛИЧЕСКАЯ -- ИОННАЯ ПРОВОДИМОСТЬ -- ПРОВОДИМОСТЬ ИОННАЯ -- Ga -- ГАЛЛИЙ -- Sr -- СТРОНЦИЙ -- ПЕРЕНОС ИОННЫЙ -- ИОННЫЙ ПЕРЕНОС
Аннотация: The maximum solid solubility of gallium in the perovskite-type La1-xSrxFe1-yGayO3-delta (x = 0.40 - 0.80; y = 0-0.60) was found to vary in the approximate range y = 0.25-0.45, decreasing when x increases. Crystal lattice of the perovskite phases, formed in atmospheric air, was studied by X-ray diffraction (XRD) and neutron diffraction and identified as cubic. Doping with Ga results in increasing unit cell volume, while the thermal expansion and total conductivity of (La, Sr)(Fe, Ga)O3-delta in air decrease with gallium additions. The average thermal expansion coefficients (TECs) are in the range (11.7-16.0) x 10(-6)K(-1) at 300-800 K and (19.3-26.7) x 10(-6)K(-1) at 800-1100 K. At oxygen partial pressures close to atmospheric air, the oxygen permeation fluxes through La1-xSrxFe1-yGayO3-delta (x = 0.7-0.8; y = 0.2-0.4) membranes are determined by the bulk ambipolar conductivity; the limiting effect of the oxygen surface exchange was found negligible. Decreasing strontium and g
allium concentrations leads to a greater role of the exchange processes. As for many other perovskite systems, the oxygen ionic conductivity of La1-xSrxFe1-yGayO3-delta increases with strontium content up to x = 0.70 and decreases on further doping, probably due to association of oxygen vacancies. Incorporation of moderate amounts of gallium into the B sublattice results in increasing structural disorder, higher ionic conductivity at temperature below 1170 K, and lower activation energy for the ionic transport

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   T 82


    Transport properties and stability of Ni-containing mixed conductors with perovskite- and K2NiF4-type structure [] = Transport properties and stability of Ni-containing mixed conductors with perovskite- and K2NiF4-type structure / V. V. Kharton, A. A. Yaremchenko, A. L. Shaula, M. V. Patrakeev, E. N. Naumovich, D. I. Logvinovich, J. R. Frade, F. M. B. Marques // Journal of Solid State Chemistry. - 2004. - V. 177, N 1. - С. 26-37. - Bibliogr.: p. 36-37 (43 ref.) . - ISSN 0022-4596

ББК 54
Рубрики: ХИМИЧЕСКИЕ НАУКИ
Кл.слова (ненормированные):
НИКЕЛАТ ЛАНТАНА -- ПЕРОВСКИТЫ -- СТРУКТУРА ТИПА K2NiF4 -- ФАЗОВОЕ РАВНОВЕСИЕ -- РАВНОВЕСИЕ ФАЗОВОЕ -- ПРОВОДИМОСТЬ -- КОЭФФИЦИЕНТ СИБЕКА -- СМЕШАННЫЕ ПРОВОДНИКИ -- ПРОВОДНИКИ СМЕШАННЫЕ -- ЭЛЕКТРОННО-ДЫРОЧНЫЙ ПЕРЕНОС -- ПЕРЕНОС ЭЛЕКТРОННО-ДЫРОЧНЫЙ -- КИСЛОРОДНАЯ ПРОНИЦАЕМОСТЬ -- ПРОНИЦАЕМОСТЬ КИСЛОРОДНАЯ -- СТРУКТУРА ТИПА ПЕРОВСКИТА
Аннотация: The total conductivity and Seebeck coefficient of a series of Ni-containing phases, including La2Ni1-xMxO4+delta (M = Co, Cu; x = 0.1-0.2) with K2NiF4-type structure and perovskite-like La0.90Sr0.10Ga0.65Mg0.15Ni0.20O3-delta and La0.50Pr0.50Ga0.65Mg0.15Ni0.20O3-delta, were studied in the oxygen partial pressure range from 10(-18) Pa to 50 kPa at 973_1223 K. Within the phase stability domain, the conductivity of layered nickelates is predominantly p-type electronic and occurs via small-polaron mechanism, indicated by temperature-activated hole mobility and p(O2) dependencies of electrical properties. In oxidizing conditions similar behavior is characteristic of Ni-containing perovskites, which exhibit, however, significant ionic contribution to the transport processes. The role of ionic conduction increases with decreasing p(O2) and becomes dominant in reducing atmospheres. All nickelate-based phases decompose at oxygen pressures considerably lower with respect to Ni/NiO
boundary. The partial substitution of nickel in La2Ni(M)O4+delta has minor effect on the stability limits, which are similar to that of La0.90Sr0.10Ga0.65Mg0.15Ni0.20O3-delta. On the contrary, praseodymium doping enhances the stability of La0.50Pr0.50Ga0.65Mg0.15Ni0.20O3-delta down to p(O2) values as low as 10(-17)-10(-10) Pa at 1023_1223 K

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   H 99


    Interfacial effects in electrochemical cells for oxygen ionic conduction measurements. III. Transference numbers vs. grain-boundary resistivity [] / V. V. Kharton, F. M. B. Marques, E. V. Tsipis, A. P. Viskup, N. P. Vyshatko, M. V. Patrakeev, E. N. Naumovich, J. R. Frade // Solid State Ionics. - 2004. - V. 168, N 1-2. - С. 137-151. - Bibliogr.: p. 151 (35 ref.) . - ISSN 0167-2738

ББК 54
Рубрики: ХИМИЧЕСКИЕ НАУКИ
Кл.слова (ненормированные):
СМЕШАННЫЕ ПРОВОДНИКИ -- ПРОВОДНИКИ СМЕШАННЫЕ -- ТВЕРДЫЕ ЭЛЕКТРОЛИТЫ -- ЭЛЕКТРОЛИТЫ ТВЕРДЫЕ -- ПИРОХЛОР -- ЭЛЕКТРОХИМИЧЕСКИЕ ЭЛЕМЕНТЫ -- ЭЛЕМЕНТЫ ЭЛЕКТРОХИМИЧЕСКИЕ -- ИОННАЯ ПРОВОДИМОСТЬ -- ПРОВОДИМОСТЬ ИОННАЯ -- ВЗАИМОДЕЙСТВИЕ МЕЖФАЗНОЕ -- МЕЖФАЗНОЕ ВЗАИМОДЕЙСТВИЕ -- КЕРАМИКА
Аннотация: Resistive grain boundaries may significantly influence transference numbers of oxygen ion-conducting ceramics due to a distinct blocking effect on the ionic transport with respect to the electronic conduction. This may lead to remarkable uncertainties, particularly in the boundary resistance estimates obtained using impedance spectroscopy without a separation of the ionic and electronic contributions, and in the interpretation of transport parameters determined by DC techniques. The role of grain boundaries was examined by the example of "pure" and SiO2-containing pyrochlore ceramics Gd2-xCaxTi2O7-delta (x = 0.05-0.14), studied at 973-1223 K using impedance spectroscopy, faradaic efficiency and e.m.f. methods. The oxygen ion transference numbers of "pure" materials in air vary in the range 0.95-0.98, increasing when temperature decreases. As expected, minor additions of SiO2 result in segregation of siliceous phase and highly resistive grain boundaries.
The total ion transference numbers of silicaenriched ceramics become considerably lower, 0.76-0.89, and increase with increasing temperature due to relatively high activation energy for the boundary resistivity; the bulk transference numbers extracted from the impedance spectroscopy and faradaic efficiency data are similar for all compositions, with and without SiO2 additions. The results, including dependence of the transport properties on oxygen pressure, suggest that a simplified description of the boundaries as a passive transport-limiting barrier is sufficiently adequate

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   M 76


    Mixed conductivity, stability and thermomechanical properties of Ni-doped La(Ga, Mg)O3-delta [] = Mixed conductivity, stability and thermomechanical properties of Ni-doped La(Ga, Mg)O3-delta / A. A. Yaremchenko, V. V. Kharton, E. N. Naumovich, D. I. Shestakov, V. F. Chukharev, A. V. Kovalevsky, A. L. Shaula, M. V. Patrakeev, J. R. Frade, F. M. B. Marques // Solid State Ionics. - 2006. - V. 177, N 5-6. - С. 549-558. - Библиогр.: с. 558 (45 назв.) . - ISSN 0167-2738

ББК 54
Рубрики: ХИМИЧЕСКИЕ НАУКИ
Кл.слова (ненормированные):
ГАЛЛАТОНИКЕЛАТЫ ЛАНТАНА -- СМЕШАННЫЕ ПРОВОДНИКИ -- ПРОВОДНИКИ СМЕШАННЫЕ -- ПЕРОВСКИТЫ -- РАВНОВЕСИЕ ФАЗОВОЕ -- ФАЗОВОЕ РАВНОВЕСИЕ -- СВОЙСТВА ТЕРМОМЕХАНИЧЕСКИЕ -- ТЕРМОМЕХАНИЧЕСКИЕ СВОЙСТВА
Аннотация: Perovskite-type LaGa0.65Mg0.15Ni0.20O3-delta exhibiting oxygen transport comparable to that in K2NiF4-type nickelates was characterized as a model material for ceramic membrane reactors, employing mechanical tests, dilatometry, oxygen permeability and faradaic efficiency measurements, thermogravimetry (TG), and determination of the total conductivity and Seebeck coefficient in the oxygen partial pressure range from 10(-15) Pa to 40 kPa. Within the phase stability domain which is similar to La2NiO4+delta, the defect chemistry of LaGa0.65Mg0.15Ni0.20O3-delta can be adequately described by the ideal solution model with oxygen vacancies and electron holes to be the only mobile defects, assuming that Ni(2+) may provide two energetically equivalent sites for hole location. This assumption is in agreement with the density of states, estimated from thermopower, and the coulometric titration and TG data suggesting Ni(4+) formation in air at T < 1150 K. The hole conductivity
prevailing under oxidizing conditions occurs via small-polaron mechanism as indicated by relatively low, temperature-activated mobility. The ionic transport increases with vacancy concentration on reducing p(O2) and becomes dominant at oxygen pressures below 10(-7)-10(-5) Pa. The average thermal expansion coefficients in air are 11.9 x 10(-6) and 18.4 x 10(-6) K(-1) at 370-850 and 850-1270 K, respectively. The chemical strain of LaGa0.65Mg0.15Ni0.20O3-delta ceramics at 1073-1123 K, induced by the oxygen partial pressure variations, is substantially lower compared to perovskite ferrites. The flexural strength determined by 3-point and 4-point bending tests is 167-189 MPa at room temperature and 85-97 MPa at 773-1173 K. The mechanical properties are almost independent of temperature and oxygen pressure at p(O2) = 1-2.1 x 10(4) Pa and 773-1173 K

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