Инвентарный номер: нет.        Ю 85     Юрьева, Э. И.     Зарядовые состояния и параметры сверхтонких взаимодействий в перовските SrFeO3 [] = Charge states and hyperfine interaction parameters in perovskite SrFeO3 / Э. И. Юрьева, В. Л. Кожевников, А. Л. Ивановский // Журнал структурной химии. - 2006. - Т. 47, N 3. - 565-569: ил. - Библиогр.: с. 569 (17 назв.) . - ISSN 0136-7463ББК 54 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): ФЕРРИТ СТРОНЦИЯ -- SrFeO3 -- СТРУКТУРА ЭЛЕКТРОННАЯ -- ЭЛЕКТРОННАЯ СТРУКТУРА -- ВЗАИМОДЕЙСТВИЕ СВЕРХТОНКОЕ -- СВЕРХТОНКОЕ ВЗАИМОДЕЙСТВИЕ -- МЕТОД ДИСКРЕТНОГО ВАРЬИРОВАНИЯ -- ПЕРОВСКИТЫ Аннотация: Ab initio методом дискретного варьирования в рамках кластерной модели определены параметры электронной структуры и сверхтонких взаимодействий в перовските SrFeO3 для различных типов спиновых и зарядовых состояний. Наилучшее согласие с экспериментом достигается при учете эффекта зарядового диспропорционирования {[Fe(4+)O6](8-) + [Fe(4+)O6](8-)} -> {[Fe(3+)O6](9-) + [Fe(5+)O6](7-)}

Инвентарный номер: нет.        З-17     Зайнуллина, В. М.     Особенности электронной, магнитной структур и проводимости феррита стронция : ab initio LSDA + U подход [Текст] / В. М. Зайнуллина, М. А. Коротин, В. Л. Кожевников // Электрохимия. - 2007. - Т. 43, № 5. - С. 578-583 : рис., табл. - Библиогр.: с. 583 (16 назв.) . - ISSN 0424-8570ББК 54 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): ФЕРРИТ СТРОНЦИЯ -- ЭЛЕКТРОННАЯ СТРУКТУРА -- ДЕФЕКТЫ -- AB INITIO РАСЧЕТЫ Аннотация: С помощью первопринципного ТВ-LMTO линейного метода "muffin--tin"-орбиталей в базисе сильной связи в приближении LSDA + U детально изучены электронная магнитная структуры и особенности дефектообразования феррита стронция Sr3Fe2O6. Установлено, что Sr3Fe2O6 - антиферромагнетик G-типа с электронной структурой полупроводника. На основе ab initio LSDA + U-расчетов изучны также различные типы и конфигурации дефектов в кислородной подрешетке (кислородные вакансии, антифренкелевские дефекты) и предложена модель ионного транспорта в Sr3Fe2O6

Инвентарный номер: нет.        Z 18     Zainullina, V. M.     Electronic and magnetic structures and conductivity of strontium ferrite. An ab initio LSDA + U approach [Текст] / V. M. Zainullina, M. A. Korotin, V. L. Kozhevnikov // Russian Journal of Electrochemistry. - 2007. - Vol. 43, № 5. - С. 570-575. - Библиогр. : с. 575 (16 назв.) ББК 54 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): ФЕРРИТ СТРОНЦИЯ -- ЭЛЕКТРОННАЯ СТРУКТУРА Аннотация: Using the first-principle nonempirical linear muffin-tin orbital method in the tight-binding approximation (TB-LMTO) to the LSDA + U approximation, the electronic and magnetic structures and defect formation in strontium ferrite Sr3Fe2O6 are studied. It is found that Sr3Fe2O6 is a G type antiferromagnetic with the semiconductor electronic structure. The calculated band gap of 1.82 eV agrees well with experimental value (~2 eV). The ferrite spectrum corresponds to that of a semiconductor with a band gap of charge transfer. Iron ions in Sr3Fe2O6 are in a high-spin state and have configuration t2g↑3 eg↑2 eg↓1. The calculated local magnetic moment on the iron ions is 3.9μB. The presence of iron ions with a magnetic moment approaching 4μB in Sr3Fe2O6 is explained by strong hybridization of 3d orbitals of iron and 2p orbitals of oxygen. The high-spin state of iron ions is described by d5+d6L states with predominant contribution d6L, where L is a hole on oxygen. Based on ab initio LSDA + U calculations, various types and configurations of defects in the oxygen sublattice (oxygen vacancies, anti-Frenkel defects) are studied and a model for ionic transport in Sr3Fe2O6is proposed Полный текст

Инвентарный номер: нет.        Z 18     Zainullina, V. M.     Electronic structure and properties of strontium ferrite Sr3Fe2O6 [Text] / V. M. Zainullina, M. A. Korotin, V. L. Kozhevnikov // European Physical Journal B: Condensed Matter Physics. - 2006. - Vol. 49, № 4. - P425-431. - Библиогр. : с. 431 (18 назв.) ББК 54 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): ЭЛЕКТРОННАЯ СТРУКТУРА -- ФЕРРИТ СТРОНЦИЯ Аннотация: The electronic structure of strontium ferrite Sr3Fe2O6 was calculated using the tight-binding linear muffin-tin orbital method (TB LMTO) in the local spin density approximation of density functional theory with Coulomb correlations correction (LSDA+U). The semiconducting character of the spectrum with charge transfer energy gap of 1.82 eV was obtained in reasonably good agreement with experimental data. The iron ions are found to be in the high spin state. The calculated value of the local spin magnetic moment of Fe3+ ion is 3.94 μB which is not typical for trivalent iron ion in the high spin state. It is shown that the strong hybridization between Fe3d and O2p orbitals favors the d6L configuration of Fe3+ ion, where L is a hole in the oxygen p shell. The mechanism of oxygen transport in ferrite is discussed basing on the total energy calculations of the different spatial configurations of oxygen vacancies Полный текст

Инвентарный номер: нет.        Y 95     Yuryeva, E. I.     Charge states and hyperfine interaction parameters in perovskite SrFeO3 [Текст] / E. I. Yuryeva, V. L. Kozhevnikov, A. L. Ivanovskii // Journal of Structural Chemistry. - 2006. - Vol. 47, № 3. - С. 553-557. - Библиогр. : с. 557 (17 назв.) ББК 54 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): ФЕРРИТ СТРОНЦИЯ -- ПЕРОВСКИТЫ -- ЭЛЕКТРОННАЯ СТРУКТУРНАЯ Аннотация: The parameters of the electronic structure and hyperfine interactions in perovskite SrFeO3 were determined for different types of spin and charge states by ab initio discrete variations within the cluster model. The best agreement with experiment was achieved when the charge disproportionation effect {[Fe4+O6]8– +[Fe4+O6]8–} ������ {[Fe3+O6]9– + [Fe5+O6]7–} was taken into account Полный текст

Инвентарный номер: нет.        I-76         Ion-electron transport in strontium ferrites: relationships with structural features and stability [Text] / M. V. Patrakeev, I. A. Leonidov, V. L. Kozhevnikov, V. V. Kharton // Solid State Sciences. - 2004. - Vol. 6, № 9. - P907-913. - Bibliogr. : p. 913 (27 ref.) ББК 54 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): ФЕРРИТ СТРОНЦИЯ -- НЕСТЕХИОМЕТРИЯ КИСЛОРОДНАЯ -- ПРОВОДИМОСТЬ ИОННАЯ -- ИОННЫЙ ПЕРЕНОС -- ЭЛЕКТРОННЫЙ ТРАНСПОРТ Аннотация: The total electrical conductivity of strontium ferrites, including intergrowth Sr4Fe6O13+delta, Sr3Fe2O6+delta with a Ruddlesden-Popper??structure, and SrFeO2.5+delta where the cubic perovskite lattice transforms into vacancy-ordered brownmillerite at p(O2) < 10 Pa and??T < 850 .C, was measured at 650.1000 .C in the oxygen partial pressure range 10.15 Pa to 50 kPa. The data were used in order to determine partial ion, p- and n-type electron contributions in the vicinity of electron.hole equilibrium point. The ferrites with brownmillerite and Ruddlesden-Popper structures exhibit substantial ion transport due to thermally-activated disordering of oxygen vacancies and??oxygen ions in the perovskite structural slabs, whereas the ion conductivity of Sr4Fe6O13+delta remains below 0.01 S cm.1 in the studied??conditions. The bonding energy of oxygen ions, evaluated from the formation enthalpy of n-type charge carriers, increases in the sequence??Sr4Fe6O13+delta < SrFeO3+delta < Sr3Fe2O6delta. These values correlate with thermodynamic stability of strontium ferrites at low p(O2). The??transition of SrFeO2.5+delta brownmillerite into disordered cubic phase above 850 .C leads to higher stability in reducing atmospheres. The??level of p-type conductivity is mainly governed by the concentration of electron holes, which was calculated from the oxygen content??determined by coulometric titration technique. The hole mobility, which is quite similar for all strontium ferrites and has a temperatureactivated??character, varies in the range 0.005.0.05 cm2 V.1 s.1 indicative of small-polaron conduction mechanism \\\\Expert2\\nbo\\Solid State Sciences\\2004, v.6, N 9, p.907.pdf

Инвентарный номер: нет.        С 87         Структура, нестехиометрия и термодинамические характеристики кислорода в феррите стронция SrFe1-xNbxO3-дельта = The Structure, Nonstoichiometry, and Thermodynamic Characteristics of Oxygenin Strontium Ferrite Doped with Niobium, SrFe1 – xNbxO3 – / П. В. Аникина, А. А. Марков, М. В. Патракеев, И. А. Леонидов, В. Л. Кожевников // Журнал физической химии. - 2009. - Т. 83, № 5. - С. 811-817 : табл., граф. - Библиогр.: с. 817 (14 назв.) . - ISSN 0044-4537ББК 54 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): ХИМИЧЕСКАЯ ТЕРМОДИНАМИКА -- ХИМИЧЕСКАЯ ТЕРМОХИМИЯ -- КИСЛОРОД -- НЕСТЕХИОМЕТРИЯ -- ФЕРРИТ СТРОНЦИЯ Аннотация: Изучено влияние допирования ниобием феррита стронция SrFe1-xNbxO3-дельта, где x=0.05, 0.1, 0.2, 0.3, 0.4, на структурные характеристики и кислородную нестехиометрию. Методом кулонометрического титрования получены диаграммы содержания кислорода в допированных производных в зависимости от температуры (650-950°C) и парциального давления кислорода в газовой фазе (10-4 - 1 атм). Рассчитаны парциальные модальные энтальпии, дельтаHo (x, дельта), и энтропии, дельтаSo (x, дельта), кислорода в SrFr1-xNbO3-дельта. На основе анализа зависимостей дельтаSo (x, дельта) сделан вывод о том, что модель случайного распределения ионов и вакансий по доступным позициям в кислородной подрешетке позволяет удовлетворительно описать экспериментальные данные. Установлено, что увеличение парциальной энтальпии дельтаHo (x, дельта) с уменьшением нестехиометрии дельта указывает на наличие слабого репульсивного взаимодействия ионов кислорода в структуре SrFe1-xNbxO3-дельта

Инвентарный номер: нет.        S 89         Structural features, nonstoichiometry and high-temperature transport in SrFe1-xMoxO3-delta / A. A. Markov, O. A. Savinskaya, M. V. Patrakeev, A. P. Nemudry, I. A. Leonidov, Yu. T. Pavlyukhin, A. V. Ishchenko, V. L. Kozhevnikov // Journal of Solid State Chemistry. - 2009. - Vol. 182, № 4. - P799-806 : il. - Bibliogr. : p. 806 (29 ref.) ББК 54 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): ФЕРРИТ СТРОНЦИЯ -- ПЕРОВСКИТЫ -- НЕСТЕХИОМЕТРИЯ -- РАСТВОРЫ ТВЕРДЫЕ -- ПРОВОДИМОСТЬ Аннотация: The oxide solid solutions SrFe1-xMoxO3-delta, where x=0.05, 0.1 and 0.2, are studied in this work. It is shown that substitution of iron for molybdenum results in stabilization of a cubic quasi-perovskite locally inhomogeneous structure, which is evidenced by HREM and Mossbauer spectroscopy. The coulometric titration is used in order to determine changes of oxygen nonstoichiometry in the obtained solutions with temperature and ambient oxygen partial pressure. Partial molar thermodynamic functions of the labile oxygen are calculated from the measured data. The variations of partial molar entropy with oxygen content follow the ideal gas model reasonably well thus demonstrating approximately random distribution of oxygen vacancies in the doped ferrite at high temperatures. The partial molar enthalpy is found to increase with doping, which is indicative of a progressive decrease in average values of the bonding energy of labile oxygen ions. The measurements of total conductivity are used in order to determine partial contributions of charge carriers. The oxygen ion component is shown to increase at small level of doping, x=0.05 while further increase in molybdenum content is accompanied with the decline in the ion conductivity. The electron contribution in reducing conditions tends to increase with molybdenum content, which is interpreted as a manifestation of involvement of Mo(5+) cations in electron transport. Concentration and mobility of electron carriers are calculated. Some increase in mobility of electron holes at small doping is explained as related to the filling of oxygen vacancies

Инвентарный номер: нет.        O-97         Oxygen nonstoichiometry and ion-electron transport in SrFe0.9M0.1O3-delta (M = Cr, Ti, Al) / M. V. Patrakeev, I. A. Leonidov, V. L. Kozhevnikov, V. V. Kharton // Materials Science Forum. - 2006. - vol. 514-516. - P382-386 : il. - Bibliogr. : p. 386 (9 ref.) ББК 54 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): ПРОВОДИМОСТЬ ИОННАЯ -- ФЕРРИТ СТРОНЦИЯ -- НЕСТЕХИОМЕТРИЯ КИСЛОРОДНАЯ Аннотация: The total conductivity and oxygen deficiency of partially substituted strontium ferrite,??SrFe0.9M0.1O3-д (M=Cr, Ti, Al), at 700-950°C were measured depending on oxygen partial pressure??varying in ranges 10-19-0.5 and 10-5-0.5 atm. The partial contributions of n- and p-type electronic??charge carriers and oxygen ions to the electrical transport were determined analyzing the total??conductivity vs. oxygen pressure dependencies. Additions of all dopants studied in this work are??found to extend the cubic perovskite phase stability range and to improve oxygen transport in the??intermediate-temperature range. The behavior of hole mobility suggests a polaron conduction??mechanism. Doping with aluminum has a weak influence on the mobility level, while the??incorporation of Cr and Ti cations into the ferrite lattice decreases hole mobility up to four times

Инвентарный номер: нет.        L 55     Leonidov, I. A.     The Thermodynamic Properties of Weakly Bound Oxygen and Electron Transport in Sr3Fe2O6 +δ under Oxidizing Conditions / I. A. Leonidov, M. V. Patrakeev, V. L. Kozhevnikov // Russian Journal of Physical Chemistry. - 2006. - Vol. 80, № 4. - P. 523-528 : ил. - Bibliogr. : p. 528 (14 ref.) ББК 54 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): СВОЙСТВА ТЕРМОДИНАМИЧЕСКИЕ -- ОКСИДЫ -- ЭЛЕКТРОННЫЙ ТРАНСПОРТ -- ПЕРОВСКИТЫ -- ФЕРРИТ СТРОНЦИЯ Аннотация: The content of oxygen, electrical conductivity, and thermal electromotive force were measured for ferrite Sr3Fe2O6+delta over the oxygen partial pressure range 10(-4)-0.5 atm at 650-950C. The partial molar thermodynamic functions of weakly bound oxygen in the oxide structure were determined. Labile oxygen ions were characterized as an ensemble of weakly interacting particles. The predominant charge carriers under experimental conditions were electron holes. An analysis of conductivity was performed using the data on the oxygen content. The concentration, activation energy, and mobility of charge carriers were determined. The results can be satisfactorily interpreted using the polaron transfer model of conductivity taking into account the charge disproportionation reaction for iron ions, 2Fe(4+)=Fe(3+)+Fe(5+) Полный текст

Инвентарный номер: нет.        S 89         Structural features and enhanced high-temperature oxygen ion transport in SrFe1-xTaxO3-delta / A. A. Markov, E. V. Shalaeva, A. P. Tyutyunnik, V. V. Kuchin, M. V. Patrakeev, I. A. Leonidov, V. L. Kozhevnikov // Journal of Solid State Chemistry. - 2013. - Vol. 197. - P191-197 : il. - Bibliogr. : p. 197 (31 ref.) ББК 54 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): ФЕРРИТ СТРОНЦИЯ -- ИОННЫЙ ПЕРЕНОС -- ПЕРОВСКИТЫ ДВОЙНЫЕ -- КИСЛОРОДНАЯ НЕСТЕХИОМЕТРИЯ Аннотация: Structural features, oxygen non-stoichiometry and transport properties are studied in the oxide series SrFe1−xTaxO3−δ, where x=0.2, 0.3 and 0.4. X-ray diffraction and electron microscopy data evidence formation of the inhomogeneous materials at x=0.3 and 0.4, which include phase constituents with a cubic perovskite and a double perovskite structure types. The composition, the amount and the typical grain size of the phase inhomogeneities are shown to depend both on doping and oxygen content. The increased oxygen-ion conductivity is observed in oxygen depleted materials, which is explained by the increase in the amount of cubic perovskite-like phase and development of interfacial pathways favorable for enhanced oxygen ion transport Полный текст

Инвентарный номер: нет.        T 44         The Structure, Nonstoichiometry, and Thermodynamic Characteristics of Oxygen in Strontium Ferrite Doped with Niobium, SrFe1-xNbxO3-δ / P. V. Anikina, A. A. Markov, M. V. Patrakeev, I. A. Leonidov, V. L. Kozhevnikov // Russian Journal of Physical Chemistry A. - 2009. - Vol. 83, № 5. - P699-704 : il. - Bibliogr. : p. 704 (14 ref.) ББК 54 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): НЕСТЕХИОМЕТРИЯ -- КИСЛОРОД -- ФЕРРИТ СТРОНЦИЯ -- ДОПИРОВАНИЕ -- НИОБИЙ Аннотация: The influence of doping with niobium on the structure and oxygen nonstoichiometry of strontium ferrite SrFe1 –xNbxO3 –δ(x= 0.05, 0.1, 0.2, 0.3, and 0.4) was studied. The content of oxygen in the doped derivatives was determined by coulometric titration as a function of temperature (650–950°C) and oxygen partialpressure in the gas phase (10–4–1 atm). The partial molar enthalpies ΔΉo(x,δ) and entropies ΔSo(x,δ) of oxygen in SrFr1−xNbxO3 –δ were calculated. An analysis of ΔSo(x,δ) dependences showed that the model of a random distribution of ions and vacancies over accessible sites in the oxygen sublattice allowed the experimental data to be described satisfactorily. An increase in the partial enthalpy ΔHo(x,δ) as nonstoichiometry δ decreased was indicative of weak repulsive interactions between oxygen ions in the structure of SrFe1 –xNbxO3 –δ Полный текст