Центральная Научная Библиотека УрО РАН

Вид документа : Статья из журнала
Шифр издания : 54/A 57
Автор(ы) : Zubkov V. G., Tyutyunnik A. P., Berger I. F., Maksimova L. G., Denisova T. A., Polyakov E. V.
Заглавие : Anhydrous tin and lead hexacyanoferrates (II)/ Part 1. Synthesis and crystal structure
Место публикации : Solid State Sciences. - 2001. - V. 3, N 3. - С. 361-367. - ISSN 1293-2558. - ISSN 1293-2558
ББК : 54
Предметные рубрики: ХИМИЧЕСКИЕ НАУКИ
Ключевые слова (''Своб.индексиров.''): олово--свинец--pb--sn--fe--железо--гексацианоферраты--синтез--кристаллическая структура--структура кристаллическая--атомы--нейтронная дифракция--дифракция нейтронная--порошковая дифракция--дифракция порошковая
Аннотация: The crystal structure of Pb2Fe(CN)6 has been first determined and refined using the Rietveld method with combined Cu---Kalpha1 X-ray and constant-wavelength neutron powder difraction data in space group P-3 (147, Z = 1). The unit cell constants are a = 7.1346(1) and 7.1805(1) A, c = 5.4531(2) and 5.3639(1) A, respectively. The compounds are layered, groups of three nearest [Fe(CN)6](4-)-complexes are joined to layers by means of Pb or Sn atoms. The same Pb or Sn atoms (c.n. = 3+3) joint three nearest complexes from the next layer. The jointing goes through 'nitrogen---lead(tin)---nitrogen' bonds
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Вид документа : Статья из журнала
Шифр издания : 54/B 39
Автор(ы) : Gushchin B. B., Milova G. D., Bazuev G. V., Lebedev V. A.
Заглавие : Behavior of materials based on tin dioxide in molten cryolite-oxyfluoride
Место публикации : Melts. - 1992. - March. - С. 486-490
Примечания : Bibliogr.: 13 ref.
ББК : 54
Предметные рубрики: ХИМИЧЕСКИЕ НАУКИ
Ключевые слова (''Своб.индексиров.''): стойкость коррозионная--коррозионная стойкость--диоксид олова--криолиты--оксифлюориды--электроды--алюминий--al--sn--олово--расплавы--электрохимические свойства--свойства электрохимические
Аннотация: The corrosion resistance and electrochemical behavior of material based on tin dioxide in molten cryolite-oxyfluoride are investigated. SnO2-based electrodes are used to measure the emf of the electrochemical concentration cell
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Вид документа : Статья из журнала
Шифр издания : 54/В 75
Автор(ы) : Воробьев Ю. П., Бамбуров В. Г.
Заглавие : Дефекты элементарной ячейки и магнитное разупорядочениев гранатах Y3-xCaxFe5-xMxO12 (M = Si, Ge)
Параллельн. заглавия :Defects of an Elementary Cell and Magnetic Disordering of Yttrium-Iron Garnet by Incorporated of Nonmagnetic Irons Ca, Si, Ge
Место публикации : Доклады Академии наук. - 2000. - Т. 375, N 6. - С. 786-790. - ISSN 0869-5652. - ISSN 0869-5652
Примечания : Библиогр.: 15 назв.
ББК : 54
Предметные рубрики: ХИМИЧЕСКИЕ НАУКИ
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Вид документа : Статья из журнала
Шифр издания : 54/H 99
Автор(ы) : Zuev M. G., Arkhipova E. V., Perelyaeva L. A., Zolotukhina L. V., Lapina O. B., Pletnev R. N.
Заглавие : Influence of Oxygen Nonstoichiometry on the Special Properties of Solid Solutions LaNb2-2xTa2xVO9-delta (x = 0-0.4) and LaTa2-2xNb2xVO9-delta (x = 0-0.1)
Место публикации : Journal of Solid State Chemistry. - 2002. - V.167, N 1. - С. 73-79. - ISSN 0022-4596. - ISSN 0022-4596
ББК : 54
Предметные рубрики: ХИМИЧЕСКИЕ НАУКИ
Аннотация: Phase equilibria in the LaVO4-Nb2O5-Ta2O5 system were analyzed. New solid solutions LaTa2-2xNb2xVO9-delta (x = 0-0.1) and LaNb2-2xTa2xVO9-delta (x = 0-0.4) were detected in this system. The structures of the vanadate-niobate LaNb2VO9 and vanadate-tantalate LaTa2VO9 are not known. The structures of the vanadate-tantalate LaTa2VO9 and LaTa2VO9-based solid solutions are similar to the structure of LaTa7O19, which refers to the hexagonal crystal system. The influence of the oxygen nonstoichiometry delta (x) on crystallochemical characteristics and spectral properties of these solid solutions were examined by the X-ray phase analysis, IR and radio spectroscopic methods. A correlation between the nonstoichiometry delta (x) and the volume of a unit cell V(x) of solid solutions LaTa2-2xNb2xVO9-delta was found. The IR spectrum of LaTa2VO9-delta transformed in going from delta = 0 to delta # 0. Two types of VO4 tetrahedra were formed in solid solutions LaNb2-2xTa2xVO9-delta dependingon delta (x)
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Вид документа : Статья из журнала
Шифр издания : 54/P 45
Автор(ы) : Kharton V. V., Shaulo A. L., Viskup A. P., Avdeev M., Yaremchenko A. A., Patrakeev M. V., Kurbakov A. I., Naumovich E. N., Marques F. M. B.
Заглавие : Perovskite-like system (Sr, La)(Fe, Ga)O3-delta: structure and ionic transport under oxidizing conditions
Место публикации : Solid State Ionics. - 2002. - V. 150, N 3-4. - С. 229-243. - ISSN 0167-2738. - ISSN 0167-2738
Примечания : Bibliogr.: p. 243 (50 ref.)
ББК : 54
Предметные рубрики: ХИМИЧЕСКИЕ НАУКИ
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 gallium 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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Вид документа : Статья из журнала
Шифр издания : 54/H 99
Автор(ы) : Yaremchenko A. A., Shaula A. L., Kharton V. V., Waerenborgh J. C., Rojas D. P., Patrakeev M. V., Marques F. M. B.
Заглавие : Ionic and electronic conductivity of La9.83-xPrxSi4.5Fe1.5O26 + or - delta apatites
Параллельн. заглавия :Ionic and electronic conductivity of La9.83-xPrxSi4.5Fe1.5O26 + or - delta apatites
Место публикации : Solid State Ionics. - 2004. - V. 171, N 1-2. - С. 51-59. - ISSN 0167-2738. - ISSN 0167-2738
Примечания : Библиогр.: с. 59 (30 назв.)
ББК : 54
Предметные рубрики: ХИМИЧЕСКИЕ НАУКИ
Аннотация: The incorporation of praseodymium in the apatite-type lattice of La9.83-xPrxSi4.5Fe1.5O26 + or - delta (x = 0-6) decreases the unit cell volume, suppresses Fe4+ formation according to Mossbauer spectroscopy, and increases p- and n-type electronic contributions to total conductivity, studied by the impedance spectroscopy and modified faradaic efficiency (FE) and electromotive force (EMF) methods at 973-1223 K. The additions of praseodymia have no essential effect on the ionic transport, with an activation energy of 99-109 kJ/mol, under oxidizing conditions. Contrary to the Al-containing analogue, La9.83Si4.5Al1.5O26, exhibiting p(O2)-independent conductivity at oxygen pressures from 10(-20) to 0.5 atm, the ionic conductivity of La9.83-xPrxSi4.5Fe1.5O26 + or - delta decreases on reducing p(O2) below 10(-14)-10(-12) atm. The observed behavior suggests a presence of hyperstoichiometric oxygen, critical for the level of ionic conduction and compensated by the formation of Fe4+ or Pr4+. The ion transference numbers in air vary in the range 0.979-0.994 for La9.83-xPrxSi4.5Fe1.5O26+delta, whilst for La9.83Si4.5Al1.5O26 the p-type electronic contribution to the total conductivity is lower than 0.5%. The average thermal expansion coefficients (TECs) of silicate-based solid electrolytes are (8.8-9.4)x10(-6)K(-1) at 300-1200 K and (14.2-15.8)x10(-6)K(-1) at 1200-1350 K
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Вид документа : Статья из журнала
Шифр издания : 54/O-97
Автор(ы) : Kharton V. V., Shaula A. L., Patrakeev M. V., Waerenborgh J. C., Rojas D. P., Vyshatko N. P., Tsipis E. V., Yaremchenko A. A., Marques F. M. B.
Заглавие : Oxygen Ionic and Electronic Transport in Apatite-Type Solid Electrolytes
Параллельн. заглавия :Oxygen Ionic and Electronic Transport in Apatite-Type Solid Electrolytes
Место публикации : Journal of the Electrochemical Society. - 2004. - V. 151, N 8. - С. A1236-A1246. - ISSN 0013-4651. - ISSN 0013-4651
Примечания : Библиогр.: с. A1246 (35 назв.)
ББК : 54
Предметные рубрики: ХИМИЧЕСКИЕ НАУКИ
Аннотация: The oxygen ionic conductivity of apatite-type La9.83Si4.5Al1.5-yFeyO26 + - delta (y = 0-1.5), La10-xSi6-yFeyO26 + - delta (x = 0-0.77; y = 1-2), and La7-xSr3Si6O26 + - delta (x = 0-1) increases with increasing oxygen content. The ion transference numbers, determined by faradaic efficiency measurements at 973-1223 K in air, are close to unity for La9.83Si4.5Al1.5-yFeyO26 + - delta and La10Si5FeO26.5, and vary in the range 0.96-0.99 for other compositions. Doping of La9.83(Si, Al)6O26 with iron results in an increasing Fe4+ fraction, which was evaluated by Mossbauer spectroscopy and correlates with partial ionic and p-type electronic conductivities, whereas La-stoichiometric La10(Si, Fe)O26 + delta apatites stabilize the Fe3+ state. Among the studied materials, the highest ionic and electronic transport is observed for La10Si5FeO26.5, where oxygen interstitials are close neighbors of Si-site cations. Data on transference numbers, total conductivity, and Seebeck coefficientas a function of the oxygen partial pressure confirm that the ionic conduction in Fe-substituted apatites remains dominant under solid oxide fuel cell operation conditions. However, reducing p (O2) leads to a drastic decrease in the ionic transport, presumably due to a transition from the prevailing interstitial to a vacancy diffusion mechanism, which is similar to the effect of acceptor doping. Iron additions improve the sinterability of silicate ceramics, increase the n-type electronic conductivity at low p(O2), and probably partly suppress the ionic conductivity drop. The thermal expansion coefficients of apatite solid electrolytes in air are (8.8-9.9)x10(-6) K(-1) at 300-1250 K
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Вид документа : Статья из журнала
Шифр издания : 54/Э 45
Автор(ы) : Еняшин А. Н., Медведева Н. И., Медведева Ю. Е., Ивановский А. Л.
Заглавие : Электронная структура и магнитные состояния кристаллической и фуллереноподобной форм дихлорида никеля NiCl2
Место публикации : Физика твердого тела. - 2005. - Т. 47, N 3. - С. 509-511: ил. - ISSN 0367-3294. - ISSN 0367-3294
Примечания : Библиогр.: с. 511 (12 назв.)
ББК : 54
Предметные рубрики: ХИМИЧЕСКИЕ НАУКИ
Ключевые слова (''Своб.индексиров.''): nicl2--электронная структура--структура электронная--дихлорид никеля--спиновая плотность--плотность спиновая--магнитные свойства--свойства магнитные--кристаллы--фуллерены--наночастицы
Аннотация: В рамках функционала локальной спиновой плотности (LSDA) изучены электронная структура и магнитные свойства кристаллической и фуллереноподобной форм дихлорида никеля NiCl2. Показано, что учет магнитного упорядочения позволяет воспроизвести запрещенную щель в зонном спектре NiCl2, а метамагнитная природа дихлорида (переход АФМ - ФМ в слабом поле) объясняется малой (0.025 eV/cell) разностью полных энергий ферромагнитной и антиферромагнитной фаз. Полиэдрические трехслойные наночастицы NiCl2 являются магнитными (магнитные моменты Ni составляют 2.0-2.3muB). Для изоструктурных наночастиц FeCl2 магнитные моменты Fe возрастают до 4.2-4.5muB, тогда как частицы CdCl2 немагнитны. Анализ межатомных взаимодействий указывает на возможность отклонения состава дихлоридных фуллереноподобных наночастиц от \glqq стехиометрического\grqq 1 : 2
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Вид документа : Статья из журнала
Шифр издания : 54/L 27
Автор(ы) : Packer R. J., Skinner S. J., Yaremchenko A. A., Tsipis E. V., Kharton V. V., Patrakeev M. V., Bakhteeva Yu. A.
Заглавие : Lanthanum substituted CeNbO4+delta scheelites: mixed conductivity and structure at elevated temperatures
Место публикации : Journal of Materials Chemistry. - 2006. - Vol. 16, № 34. - С. 3503-3511
Примечания : Библиогр. : с. 3511 (17 назв.)
ББК : 54
Предметные рубрики: ХИМИЧЕСКИЕ НАУКИ
Ключевые слова (''Своб.индексиров.''): лантан--проводимость--стехиометрия--церий
Аннотация: CeNbO4+d is a room temperature monoclinic material exhibiting a phase change to a tetragonal scheelite polymorph at 1023 K. The material can accommodate oxygen excess up to a composition of CeNbO4.25 in air which is believed to be incorporated on interstitial sites and hence is of interest for solid oxide fuel cell applications. Recent research however pointed to poor stability at low p(O2) making optimisation a necessity. To this end the effect of substituting lanthanum for cerium in CeNbO4+d has been investigated in terms of redox, structural and mixed conductive behaviour. On increasing lanthanum content the overall oxygen hyperstoichiometry of the as-prepared substituted phases was found to decrease. A reduction in the temperature of the monoclinic fergusonite to tetragonal scheelite phase transformation with increasing lanthanum content was also observed. However, the extent of oxidation with increasing temperature was found to decrease. Four probe dc conductivity measurements in the temperature range 923 K to 1223 K showed that the total conductivity decreased and that the p(O2) dependence of the total ionic conductivity increased with increasing lanthanum content. The ionic transference number, ti, was found to increase to a maximum of approximately 0.75 with lanthanum substitution but at low p(O2) the stability of the tetragonal phase was found to decrease
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10.

Вид документа : Статья из журнала
Шифр издания : 54/V 86
Автор(ы) : Volkov V. L., Podval'naya N. V.
Заглавие : Thermal expansion and electrical conductivity of M4±xV6O16±x (M = K, Rb, Cs) polyvanadates
Место публикации : Inorganic Materials. - 2008. - Vol. 44, № 2. - С. 176-180
Примечания : Библиогр.: с. 179-180 (11 назв.)
ISSN: 0020-1685
ББК : 54
Предметные рубрики: ХИМИЧЕСКИЕ НАУКИ
Ключевые слова (''Своб.индексиров.''): термическое расширение--поливанадаты--электропроводность--стехиометрия
Аннотация: The thermal expansion coefficient of the M4±xV6O16±x(M = K, Rb, Cs) polyvanadates is a nonmonotonic function of temperature, with sharp minima at 663, 558, and 713 K, respectively, which are accompanied by no changes in cell symmetry (tetragonal) or a /c axial ratio. The polyvanadates are shown to be ionic–electronic conductors. The activation energy for electronic conduction in the three polyvanadates is 0.43±0.02eV. In the range 675–740 K, the conductivity of K4.2V6O16.2 shows metallic behavior. Rubidium polyvanadate has a narrower temperature range of unactivated conduction, and Cs3.8V6O15.8 has no such range. The conclusion is made that these phases undergo cation disordering due to deviations from the M4V6O16 stoichiometry
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11.

Вид документа : Статья из журнала
Шифр издания : 54/P 56
Автор(ы) : Gromilov S. A., Korolkov I. V., Yusenko K. V., Korenev S. V., D'yachkova T. V., Zainullin Yu. G., Tyutyunnik A. P.
Заглавие : Phase transformations of the Re0.3Ir0.7 solid solution
Место публикации : Journal of Structural Chemistry. - 2005. - Vol. 46, № 3. - С. 474-478
Примечания : Библиогр. : с. 478 (9 назв.)
ББК : 54
Предметные рубрики: ХИМИЧЕСКИЕ НАУКИ
Ключевые слова (''Своб.индексиров.''): иридий--родий--рентгенофазовый анализ--кристаллохимия
Аннотация: Transformations of the nonequilibrium solid solution Re0.3Ir0.7 at increased pressure (1-10 GPa) and temperature (2000C) have been studied. A phase transition from the hexagonal close-packed cell to the face-centered cubic cell without a loss of density and volume per atom has been detected
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12.

Вид документа : Статья из журнала
Шифр издания : 54/C 91
Автор(ы) : Voronin V. I., Ponosov Yu. S., Berger I. F., Proskurnina N. V., Zubkov V. G., Tyutyunnik A. P., Bushmeleva S. N., Balagurov A. M., Sheptyakov D. V., Burmakin E. I., Shekhtman G. Sh., Vovkotrub E. G.
Заглавие : Crystal structure of the low-temperature form of K3PO4
Место публикации : Inorganic Materials. - 2006. - Vol. 42, № 8. - С. 908-913: il.
Примечания : Библиогр. : с. 912-913 (15 назв.)
ISSN: 0020-1685
ББК : 54
Предметные рубрики: ХИМИЧЕСКИЕ НАУКИ
Ключевые слова (''Своб.индексиров.''): ортофосфат калия--структура кристаллическая--метод ритвельда
Аннотация: The crystal structure of the low-temperature form of K3PO4 has been determined for the first time using neutron diffraction (Rietveld method) and Raman spectroscopy: orthorhombic cell (sp. gr. Pnma, Z = 4), lattice parameters a = 1.12377(2) nm, b = 0.81046(1) nm, c = 0.59227(1) nm. The structure is made up of isolated [PO4] tetrahedra, with the potassium ions in between
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13.

Вид документа : Статья из журнала
Шифр издания : 54/S 53
Автор(ы) : Shein I. R., Ivanovskii A. L.
Заглавие : Influence of lattice vacancies on the structural, electronic, and cohesive properties of niobium and molybdenum borides from first-principles calculations
Место публикации : Physical Review B: Condensed Matter and Materials Physics. - 2006. - Vol. 73, № 14. - С. 144108/1-144108/9
Примечания : Библиогр. : с. 144108/8 (55 назв.)
ISSN: 1098-0121
ББК : 54
Предметные рубрики: ХИМИЧЕСКИЕ НАУКИ
Ключевые слова (''Своб.индексиров.''): борид молибдена--борид ниобия--первопринципные расчеты
Аннотация: The influence of lattice vacancies on the structural, cohesive, and electronic properties of Nb and Mo borides were examined by means of the full-potential linearized augmented plane wave method and the generalized gradient approximation. The structural parameters, densities of states (DOS), charge distribution, heats of formations, and vacancy formation energies for metal-deficient hexagonal Nb1−xB2, Mo1−xB2 as well as for boron-deficient rhombohedral Mo2B5−y were obtained and compared with those for complete hexagonal NbB2, MoB2 and rhombohedral Mo2B5. We show that the presence of metal vacancies in hexagonal phases leads to (i) the decreasing of in-plane parameter a but increasing the interplane cell parameter c; (ii) well pronounced changes of near-Fermi DOS and the appearance of the novel vacancy states; and (iii) a substantial decrease in the stability of borides. On the contrary, in the case of Mo2B5 the appearance of the boron vacancies leads to enhancing of stability of a rhombohedral phase
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14.

Вид документа : Статья из журнала
Шифр издания : 54/C 51
Автор(ы) : Bushkova O. V., Andreev O. L., Batalov N. N., Shkerin S. N., Kuznetsov M. V., Tyutyunnik A. P., Koryakova O. V., Song E. H., Chung H. J.
Заглавие : Chemical interactions in the cathode half-cell of lithium-ion batteries
Место публикации : Journal of Power Sources. - 2006. - Vol. 157, № 1. - С. 477-482
ББК : 54
Предметные рубрики: ХИМИЧЕСКИЕ НАУКИ
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15.

Вид документа : Статья из журнала
Шифр издания : 54/G 96
Автор(ы) : Gusev A. I., Lipatnikov V. N.
Заглавие : Ordering in the zeta-Ta4C3 – x Carbide Phase
Место публикации : JETP Letters. - 2005. - Vol. 82, № 5. - С. 287-291: il.
Примечания : Bibliogr. : p. 291 (14 ref.)
ББК : 54
Предметные рубрики: ХИМИЧЕСКИЕ НАУКИ
Ключевые слова (''Своб.индексиров.''): нестехиометрия--карбид тантала
Аннотация: The structure of the zeta-Ta4C3 – x nonstoichiometric trigonal (rhombohedral) carbide, which is formed in the tantalum–carbon system, has been analyzed by neutron diffraction, x-ray diffraction, and metallography. The ordered distributions of carbon atoms and structure vacancies have been experimentally determined and the distribution function of carbon atoms over the nonmetallic-sublattice sites, where ordering occurs, has been calculated. The parameters of the unit cell of the zeta-Ta4C3 – x (TaC0.67) trigonal (space group ) carbide are found to be aH = 0.3123 nm and cH = 3.0053 nm. It has been shown that the metallic close packed sublattice of the ??zeta-Ta4C3 – x carbide is formed by alternating blocks, where metal atoms are located both in the fcc and hcp sublattices of the TaCy cubic and Ta2C hexagonal carbides, respectively
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16.

Вид документа : Статья из журнала
Шифр издания : 54/L 79
Автор(ы) : Lipatnikov V. N., Gusev A. I.
Заглавие : Atomic–Vacancy Ordering in the arbide Phase zeta--Ta4C3 –x
Место публикации : Physics of the Solid State. - 2006. - Vol. 48, № 9. - С. 1634-1645
Примечания : Bibliogr. : p. 1645 (30 ref.)
ISSN: 1063-7834
ББК : 54
Предметные рубрики: ХИМИЧЕСКИЕ НАУКИ
Ключевые слова (''Своб.индексиров.''): карбид тантала--нестехиометрия--атомно-вакансионное упорядочение
Аннотация: The structure of the nonstoichiometric trigonal (rhombohedral) carbide zeta--Ta4C3 –x forming in the tantalum–carbon system is studied by neutron diffraction, x-ray diffraction, and metallography. The unit cell parameters of the trigonal (space group ) carbide zeta-Ta4C3 –x(TaC0.67) are found to be ah= 0.3123 nm and ch= 3.0053 nm. It is shown that the metallic close-packed sublattice of the zeta-Ta4C3 –x phase consists of alternating blocks in which the metallic atoms are arranged in the same manner as on the fcc sublattice of the cubic carbide TaCy and the hcp sublattice of the hexagonal carbide Ta2C, respectively, and that the former sublattice is intermediate between the latter two sublattices. We are the first to establish experimentally that the distribution of carbon atoms and structural vacancies in the zeta-Ta4C3 – x carbide is ordered and to calculate the istribution function of carbon atoms over the nonmetallic-sublattice sites involved in the ordering. The results obtained for the zeta-Ta4C3 – x phase are used to refine the phase diagram of the Ta–C system
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17.

Вид документа : Статья из журнала
Шифр издания : 54/O-97
Автор(ы) : Markov A. A., Patrakeev M. V., Kharton V. V., Pivak Y. V., Leonidov I. A., Kozhevnikov V. L.
Заглавие : Oxygen Nonstoichiometry and Ionic Conductivity of Sr3Fe2-xScxO7-delta
Место публикации : Chemistry of Materials. - 2007. - v.19, № 16. - С. 3980-3987
Примечания : Bibliogr. : 30 ref.
ISSN: 0897-4756
ББК : 54
Предметные рубрики: ХИМИЧЕСКИЕ НАУКИ
Ключевые слова (''Своб.индексиров.''): нестехиометрия кислородная--проводимость ионная--скандий--железо--стронций
Аннотация: The substitution of scandium for iron in the Ruddlesden-Popper Sr3Fe2-xScxO7-delta (x=0-0.3) system increases tetragonal unit-cell volume and oxygen nonstoichiometry and decreases partial p- and n-type electronic conductivities studied in the oxygen partial pressure range from 1 x 10(-20) to 0.7 atm at 973-1223 K. The solubility of Sc(3+) corresponds to approximately x ~ 0.35. The relatively low, temperatureactivated hole mobility indicates a small-polaron mechanism of the electronic transport, as for undoped Sr3Fe2O7-delta. The atomistic computer simulations showed that major contribution to the ionic conductivity is provided by the oxygen sites surrounded by iron cations in the perovskite-type layers of Sr3(Fe,Sc)2O7-delta structure, whereas stable ScO6 octahedra are essentially excluded from the oxygen diffusion processes.??Minimum migration energy, 0.9-1.4 eV, was found for nonlinear pathways formed by the apical O1??sites linking iron-oxygen polyhedra along the c-axis and equatorial O3 positions in the perovskite-type??planes. The direct O3 f O3 jumps are characterized with higher energetic barrier, 1.5-2.2 eV. Because??of the increasing concentration of vacant O3 sites induced by scandium doping, the apparent activation energy for oxygen-ionic transport decreases from about 2 eV, as observed for undoped strontium ferrite at 1123-1223 K, down to 0.95-1.15 eV for Sr3Fe2-xScxO7-delta (x = 0.2-0.3). As a result, the partial ionic conductivity of Sr3Fe1.7Sc0.3O7-delta at temperatures below 1000 K becomes higher than that in Sr3Fe2O7-delta
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18.

Вид документа : Статья из журнала
Шифр издания : 54/S 98
Автор(ы) : Zubkov V. G., Tyutyunnik A. P., Tarakina N. V., Berger I. F., Surat L. L., Slobodin B. V., Svensson G., Forslund B., Shulgin B. V., Pustovarov V. A., Ishchenko A. V., Cherepanov A. N.
Заглавие : Synthesis, crystal structure and luminescent properties of pyrovanadatesA2CaV2O7 (A јRb, Cs)
Место публикации : Solid State Sciences. - 2009. - Vol. 11. - С. P.726-732: il.
Примечания : Bibliogr. : p. 731-732 (29 ref.)
ISSN: 1293-2558
ББК : 54
Предметные рубрики: ХИМИЧЕСКИЕ НАУКИ
Ключевые слова (''Своб.индексиров.''): оксиванадат рубидия--оксиванадат цезия--пированадаты--дифрактограммы порошковые--дифрактометрия рентгеновская --дифракция электронная--фотолюминесценция
Аннотация: The novel vanadium oxides Rb2CaV2O7 and Cs2CaV2O7 have been prepared by solid-state reaction and their crystal structures determined and refined using X-ray, neutron powder and electron diffraction data. Rb2CaV2O7 and Cs2CaV2O7 are isostructural, crystallizing in space group P21/n with unit cell parameters: a= 13.8780(1), b = 5.96394(5), c = 10.3376(1) Е, beta = 104.960(1) and a= 14.0713(2),b = 6.0934(1), c=10.5944(1) A, beta = 104.608(1), respectively. Their crystal structures can be described as a framework of CaO6 octahedra and V2O7 pyrogroups with alkaline metals found in the tunnels formed. Photoluminescence (PL) and PL excitation spectra of the considered pyrovanadates have been studied in??the vacuum ultraviolet (VUV) to visible light (Vis) range as well as their pulse cathode luminescence (PCL) spectra and the kinetic parameters of PCL. In the PL and the PCL spectra of both pyrovanadates??recorded at T ј 300 K a broad band with maxima at 2.2, 2.4 eV and two shoulders (bands) at 2.0 and 2.58 eV have been observed. At Tј 10 K the band at 2.0 eV becomes the main band in the spectra. Two types of luminescence centers for each pyrovanadate, with very similar excitation bands at 3.75, 4.84, 6.2,??7.3 and 9.1 eV, have been found. The nature of the luminescence centers connected with the bands at 2.0,2.2, 2.4 and 2.58 eV is discussed
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19.

Вид документа : Статья из журнала
Шифр издания : 54/S 61
Автор(ы) : Medvedeva N.I., Shein I. R., Gutina O. Yu., Ivanovskii A. L.
Заглавие : Simulation of the Structural, Electronic, and Magnetic Propertiesof Fe3C1 –xBxBorocementites
Место публикации : Physics of the Solid State. - 2007. - Vol. 49, № 12. - С. P. 2298-2302: il.
Примечания : Bibliogr. : p. 2301-2302 (15 ref.)
ISSN: 1063-7834
ББК : 54
Предметные рубрики: ХИМИЧЕСКИЕ НАУКИ
Ключевые слова (''Своб.индексиров.''): бороцементиты--энтальпия--свойства магнитные--свойства структурные--свойства электронные
Аннотация: The structural, electronic, and magnetic properties and the enthalpy of formation of iron borocementites Fe3C1 –xBx(x= 0, 0.25, 0.50, 0.75, 1.00) are analyzed using ab initio calculations in the framework of the electron density functional theory. It is found that the unit cell parameter a of the orthorhombic lattice increases linearly and the parameters b and c decrease as the boron concentration increases. The density of states at the Fermi level changes only slightly, and the main variations in the band structure occur in the region of the bottom of the valence bands. The magnetic moment of the iron atoms and the total magnetization and stability of the Fe3C1 –xBx phases increase linearly with an increase in the boron concentration
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20.

Вид документа : Статья из журнала
Шифр издания : 54/S 53
Автор(ы) : Shein I. R., Ivanovskii A. L.
Заглавие : First principle prediction of vacancy-induced magnetism in non-magneticperovskite SrTiO3
Место публикации : Physics Letters A. - 2007. - Vol. 371. - С. P. 155-159: il.
Примечания : Bibliogr. : p. 159 (32 ref.)
ISSN: 0375-9601
ББК : 54
Предметные рубрики: ХИМИЧЕСКИЕ НАУКИ
Ключевые слова (''Своб.индексиров.''): вакансии решеток--структура электронная--магнетизм--перовскиты--srtio3
Аннотация: A theoretical study of magnetization in non-magnetic cubic perovskite SrTiO3 induced by vacancies in Sr, Ti and oxygen sublattices is presented using the full-potential linear augmented plane wave (FP-LAPW) method within the generalized gradient approximation (GGA) for the exchange correlation potential. The results show that the oxygen and titanium vacancies lead to the magnetization of non-magnetic perovskite SrTiO3 due to the spin-polarization of valence states for the Ti and O atoms, nearest to these vacancies. In result the insulating SrTiO3 becomes metallic-like with magnetic moments (per cell) 1.30 мB and 3.54 мB for non-stoichiometric SrTiO3.д and SrTi1-deltaO, respectively. On the contrary, our calculations reveal that for Sr vacancy the non-magnetic state of perovskite is retained, whereas the electronic spectrum of Sr1-deltaTiO3 also adopts metallic-like type
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