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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Удод, Любовь Викторовна, Ситников, Максим Николаевич
Заглавие : Влияние катионного замещения на полиморфные переходы в пирасаннате висмута Bi2Sn2O7
Место публикации : Вестник СибГАУ. - Красноярск: СибГАУ, 2015. - Т. 16, № 4. - С. 975-982. - ISSN 1816-9724
Примечания : Библиогр.: 53. - Работа выполнена при финансовой поддержке Российского фонда фундаментальных исследований, грант № 15-42-04099 р_сибирь_а, и государственного задания № 114090470016
Ключевые слова (''Своб.индексиров.''): полиморфные переходы--диэлектрическая проницаемость--электросопротивление--катионное замещение--дифференциальная сканирующая калориметрия--polymorphic transitions--dielectric permeability--cation substitution--electrical resistivity--differential scanning calorimetry
Аннотация: Рассмотрена разработка технологии новых сенсорных материалов, необходимых для газочувствительных приборов, применяемых в ракетостроении. Целью данной работы является изучение влияния допирования разновалентными катионами на кристаллографическую структуру, диэлектрические и электрические свойства пирохлорного соединения Bi 2Sn 2O 7, обладающего селективной избирательностью к газам. Методом твердофазного синтеза впервые синтезированы соединения Bi2(Sn1-xMex)2O7, где Me = Mn, Cr, x = 0, 0,05, находящиеся сразу в двух полиморфных модификациях - орторомбической и кубической. В твердых растворах Bi2(Sn0,95Cr0,05)2O 7 методом сканирующей калориметрии обнаружено два новых структурных перехода, по сравнению со станнатом висмута Bi2Sn2O7. Ионы Mn 4+ сместили фазовые границы полиморфных переходов в сторону меньших температур, а фазовый α→β-переход около 370 К, характерный для Bi2(Sn1-xCrx)2O7, где x = 0, 0,05, подавили почти полностью. Полиморфный переход при Т = 543 К для Bi 2(Sn0,95Mn0,05) 2O 7 протекает с выделением тепла, в отличие от Bi2(Sn1-xCrx)2O7, где x = 0, 0,05. Исследована взаимосвязь структурных, электрических и диэлектрических свойств. Установлены аномалии в температурной зависимости электросопротивления и диэлектрической проницаемости (мнимой и реальной частями) как в области низких температур, так и при высоких температурах. Эти особенности объясняются в рамках модели мартенситных фазовых переходов. Методом сканирующей калориметрии найдены температуры структурных фазовых переходов, которые коррелируют с аномалиями электросопротивления в интервале температур 300 T 1000 К для Bi2(Sn1-xCrx)2O7, x The goal of this work is to develop a new technology of sensor materials required for gas sensing devices used in missile. The aim of this work is to study the effect of doping cations with different valency on the crystallographic structure, dielectric and electrical properties of pyrochlore compound Bi2Sn2O7 with selectivity to gases. Polycrystalline compounds Bi2(Sn1-xMex)2O7, where Me = Mn, Cr, x = 0, 0.05 have been synthesized by conventional solid-state reaction. According to the X-ray powder diffraction research, our sample consists of two polymorphs phases: cubic and rhombic. Two new structural transition are found in Bi2(Sn0.95Cr0.05)2O7 solid solutions by scanning calorimetry, as compared to bismuth pyrostannate Bi2Sn2O7. Ions Mn 4+ leads to shift of phase boundary of polymorphic transitions towards lower temperatures, and the phase α→β-transition at about 370 K, which is characteristic for Bi2(Sn1-xCrx)2O7, where x = 0, 0.05 is suppressed. The polymorphic transition at T = 543 K for Bi2(Sn0.95Mn0.05)2O7 occurs with calorification, in contrast to Bi2(Sn1-xCrx)2 7, where x = 0, 0.05. The relationship between structural, electrical and dielectric properties is investigated. Anomalies in the temperature dependence of electrical resistivity and dielectric permeability (real and imaginary part) as in the low region temperatures as in the high region temperature are found. These features are explained within a model of martensitic phase transitions. The temperature of the structural phase transitions correlates with temperature of maximum of the electrical resistivity in the temperature range 300 T 1000 K for Bi2(Sn1-xCrx)2O7, x
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Романова, Оксана Борисовна, Харьков, Анатолий Михайлович, Ситников, Максим Николаевич, Кретинин В. В.
Заглавие : Переход металл-диэлектрик в катион-замещенных соединениях ReхMn1-xS (Re = Gd, Sm, Ho)
Место публикации : Вестник СибГАУ. - Красноярск: СибГАУ, 2015. - Т. 16, № 2. - С. 478-484. - ISSN 1816-9724 (Шифр В22/2015/16/2)
Примечания : Библиогр.: 38. - Работа выполнена при финансовой поддержке РФФИ № 15-42-04099 р_Cибирь_а и государственного задания № 114090470016.
Ключевые слова (''Своб.индексиров.''): сульфиды редкоземельных элементов--проводимость--переход металл-диэлектрик--термоэдс--sulfides of rare-earth elements--conductivity--transition metal-insulator--thermoelectric power
Аннотация: Представлены результаты исследования транспортных свойств катион-замещенных сульфидов RexMn1-xS (Re = Gd, Sm, Ho) с ГЦК-решеткой типа NaCl в области температур 77-1200 К. С увеличением степени катионного замещения в этих соединениях RexMn1-xS (Re = Gd, Sm, Ho) изменяется тип проводимости от полупроводникового до металлического при критической концентрации Х С. Концентрационный переход металл-диэлектрик в системе Gd XMn 1-XS сопровождается уменьшением величины удельного электросопротивления на 12 порядков и коэффициента термоЭДС (α) на два порядка. Катионное замещение в твердых растворах GdxMn1-xS приводит к смене дырочного типа проводимости (α 0), свойственного моносульфиду марганца, на электронный (α 0). Уменьшение величины α с увеличением содержания гадолиния в решетке MnS указывает на то, что Gd действует как донорная примесь. Для Sm 0,2Mn 0,8S обнаружен резкий максимум сопротивления при Т This paper presents the results of a study of the transport properties of cation-substituted sulfides Re XMn 1-XS (Re = = Gd, Sm, Ho) with FCC NaCl type in the temperature range 77-1200 K. With increasing degree of cation substitution in these compounds Re XMn 1- ХS (Re = Gd, Sm, Ho) the conductivity type changes from the semiconductor to the «metal» at the critical concentration X C. The concentration of metal-insulator transition in the system Gd XMn 1-XS is accompanied by a decreasing in the electrical resistivity of value on 12 orders and Seebeck coefficient (α) is on two orders. The cation-substitution in the solid solutions Gd XMn 1-XS leads to p-type conductivity (α 0), as comprising to electronic (α 0) for manganese monosulfide. Decrease of α with increasing gadolinium concentration in the MnS lattice indicates that the Gd acts as a donor impurity. For Sm 0,2Mn0,8S a maximum resistance at T
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Zinenko V. I., Sofronova S. N.
Заглавие : The nonempirical calculation of the cation ordering and lattice dynamics in the solid solutions of PbSc1/2Nb1/2O3 and PbSc1/2Ta1/2O3
Место публикации : 11th International Conference on Phonon Scattering in Condensed Matter (PHONONS 2004) (JUL 25-30, 2004, St Petersburg, RUSSIA): WILEY-V C H VERLAG GMBH, 2004. - P3047-3051. - ISBN 3-527-40588-7, DOI 10.1002/pssc.200405286
Примечания : Cited References: 10
Аннотация: An effective Hamiltonian for the study of Sc-Nb(Ta) cation ordering in PbSc1/2Nb(Ta)(1/2)O-3 solid solutions is written out. To determine the parameters of the effective Hamiltonian, a nonempirical calculation is performed within an ionic-crystal model taking into account the deformation, dipole and quadrupole polarizabilities of ions. The phase transition temperatures are calculated by mean field, cluster approximations and Monte-Carlo method. Within the same ionic-crystal model, we calculated the high-frequency permittivity, Born dynamic charges, and the phonon spectrum for a completely disordered and ordered phases. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zinenko V. I., Sofronova S. N.
Заглавие : Statistical mechanics of cation ordering in PbSc1/2Ta1/2O3 and PbSc1/2Nb1/2O3 solid solutions
Разночтения заглавия :авие SCOPUS: Statistical mechanics of cation ordering in PbSc1/2Ta 1/2O3 and PbSc1/2Nb1/2O3 solid solutions
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2005. - Vol. 47, Is. 12. - P2309-2314. - ISSN 1063-7834, DOI 10.1134/1.2142896
Примечания : Cited References: 17
Предметные рубрики: PHASE-TRANSITION
PEROVSKITE
DISORDER
FERROELECTRICS
CRYSTALS
MODEL
Аннотация: A model Hamiltonian for B cation ordering (Sc-Nb(Ta)) in PbSc1/2Nb1/2O3 and PbSc1/2Ta1/2O3 solid solutions is constructed. The parameters of the model Hamiltonian are determined from the ab initio calculation within the ionic crystal model with allowance made for the deformability and the dipole and quadrupole polarizabilities of the ions. The temperatures of the phase transition due to the ordering of the B cations are calculated by the Monte Carlo method in the mean-field and cluster approximations. The phase transition temperatures calculated by the Monte Carlo method (1920 K for PbSc1/2Ta1/2O3 and 1810 K for PbSc1/2Nb1/2O3) are consistent with the experimental data (1770 and 1450 K, respectively). The thermodynamic properties of the cation ordering are investigated using the Monte Carlo method. (c) 2005 Pleiades Publishing, Inc.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zinenko V. I., Sofronova S. N.
Заглавие : Statistical mechanics of cation ordering and lattice dynamics of PbZrxTi1-xO3 solid solutions
Разночтения заглавия :авие SCOPUS: Statistical mechanics of cation ordering and lattice dynamics of PbZr xTi1-xO3 solid solutions
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2004. - Vol. 46, Is. 7. - P1291-1300. - ISSN 1063-7834, DOI 10.1134/1.1778455
Примечания : Cited References: 18
Предметные рубрики: PEROVSKITE
Аннотация: An effective Hamiltonian for Zr-Ti cation ordering in PbZrxTi1 - xO3 solid solutions is written out. To determine the parameters of the effective Hamiltonian, a nonempirical calculation is performed within an ionic-crystal model taking into account the deformation and dipole and quadrupole polarizabilities of ions. The thermodynamic properties of cation ordering are studied using the Monte Carlo method. The calculated phase transition temperatures (180 and 250 K for the concentrations x = 1/3 and 1/2, respectively) are much lower than the melting temperature of the compound under study. At such temperatures, the ordering kinetics is frozen and, in reality, the phase transition to the ordered phase does not occur, in agreement with experimental observations. Within the same ionic-crystal model, we calculated the high-frequency permittivity, Born dynamic charges, and the lattice vibration spectrum for a completely disordered phase and certain ordered phases. It is shown that soft vibration modes, including ferroelectric ones, exist in the lattice vibration spectrum of both the completely disordered and the ordered phases. (C) 2004 MAIK "Nauka / Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zamkova N. G., Zhandun V. S., Zinenko V. I.
Заглавие : First-principles calculations of ferroelectric properties in AA`BB`O6 double perovskites with different types of cation ordering
Место публикации : Phys. status solidi B. - 2013. - Vol. 250, Is. 9. - P.1888-1897. - ISSN 0370-1972, DOI 10.1002/pssb.201349084
Ключевые слова (''Своб.индексиров.''): density functional theory--double perovskites--ferroelectrics--polarization
Аннотация: First-principles calculations of lattice dynamics and polarization properties have been performed for double perovskite ABiBNbO6 (A - alkali metal Na, Rb, and B - trivalent metal Sc, Lu). Three possible types of A- and B-site cation ordering are studied: layer and columnar ordering of A-site cations with rocksalt ordering of B-site cations, and layer ordering of both cations. The ground state of all compounds is polar with a large value of polarization for all types of cation ordering. For some compounds we obtain spontaneous polarization of 0.7-1.0Cm-2 that is twice the BaTiO3 value. For RbBiScNbO6 the lowest-energy state has layer ordering of both A- and B-site cations, which is rare for compounds with double-perovskite structure.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zamkova N. G., Zinenko V. I.
Заглавие : Effect of cation substitution on the lattice dynamics and ferroelectric instability of cubic BaTiO3 and BaZrO3 doped with Bi and La ions
Коллективы : Russian Foundation for Basic Research [07-02-00069]
Разночтения заглавия :авие SCOPUS: Effect of cation substitution on the lattice dynamics and ferroelectric instability of cubic BaTiO3 and BaZrO3 doped with Bi and la ions
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2009. - Vol. 51, Is. 5. - P973-981. - ISSN 1063-7834, DOI 10.1134/S1063783409050151
Примечания : Cited References: 11. - This work was supported by the Russian Foundation for Basic Research, project no. 07-02-00069.
Предметные рубрики: CERAMICS
Аннотация: The spectra of lattice vibration frequencies of solid solutions Ba1 - x Bi(2x/3)a-- Ti-x/3(Zr)O-3 and Ba1 - x La (x) Ti(Zr)(1 - x/4)a-- O-x/4(3) are calculated in terms of a generalized Gordon-Kim model with inclusion of the dipole and quadrupole polarizabilities. Over the entire concentration range, the calculated phonon spectra contain a ferroelectric soft mode. The effect of various interactions on the ferroelectric instability of these solid solutions is studied. It is shown that the character of ferroelectric instability is largely determined by the mechanism of charge compensation.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vasiliev A. D., Golovnev N. N.
Заглавие : Structure of the oxonium compound of pefloxacinium hexachloridostannate(IV)
Коллективы : Ministry of Education of the Russian Federation [4.7666.2017/BCh]; Siberian Federal University [4.7666.2017/BCh]
Место публикации : J. Struct. Chem. - 2018. - Vol. 59, Is. 3. - P.641-645. - ISSN 0022-4766, DOI 10.1134/S0022476618030198. - ISSN 1573-8779(eISSN)
Примечания : Cited References: 13. - The work was performed within the State Contact of the Ministry of Education of the Russian Federation and the Siberian Federal University in 2017-2019 (4.7666.2017/BCh)
Предметные рубрики: ANTIBACTERIAL AGENTS
QUINOLONE
Ключевые слова (''Своб.индексиров.''): pefloxacinium cation--oxonium cation--chloride ion--hexachloridostannate(iv) anion--ionic compound--crystal structure
Аннотация: The structure of tris{hexachloridostannate(IV)}-hexachloride-tetrakis(pefloxacinium)-tetraoxonium undecahydrate (CCDC 1551760) 4PefH 3 2+ , 4H3O+, 3SnCl 6 2− , 6Cl−, 11H2O (I), (PefH is pefloxacin) is determined. The I crystals are triclinic: a = 13.5474(10) Å, b = 15.2859(11) Å, c = 15.6586(11) Å, α = 94.467(1)°, β = 105.477(1)°, γ = 111.560(1)°, V = 2849.9(4) Å3, space group Pī, Z = 1. The structure is stabilized by multiple intermolecular hydrogen bonds and π–π-interactions between the PefH32+ ions.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vasiliev A. D., Golovnev N. N.
Заглавие : Crystal structure of two ionic sparfloxacin compounds
Место публикации : J. Struct. Chem.: MAIK Nauka-Interperiodica / Springer, 2015. - Vol. 56, Is. 5. - P.907-911. - ISSN 00224766 (ISSN), DOI 10.1134/S0022476615050121
Примечания : Cited References: 20
Предметные рубрики: ANTIBACTERIAL AGENTS
QUINOLONE
MONOHYDRATE
COMPLEXES
Ключевые слова (''Своб.индексиров.''): crystal structure--hydrogen bonds--sparfloxacindi-ium cation--zinc and cadmium tetrahalide anions--π-π interaction
Аннотация: The structure of two new ionic compounds of sparfloxacin (C19H22F2N4O3, SfH), SfH3[ZnCl4]•1.5H2O (I) and SfH3[CdBr4]•H2O (II), is determined. Crystallographic data are as follows: for I a = 14.505(3) Å, b = 12.615(3) Å, c = 29.118(7) Å, V = 5254(4)Å3, space group Pbca, Z = 8; for II a = 13.2822(5) Å, b = 10.2564(4) Å, c = 21.3250(8) Å, β = 100.7248(4)°, V = 2854.3(3) Å3, space group P21/ n, Z = 4. The structures of the compounds are stabilized by intra- and intermolecular hydrogen bonds and the structure of I is additionally stabilized by the π-π interaction between the SfH 3 2+ ions. © 2015 Pleiades Publishing, Ltd.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vasiliev A. D., Golovnev N. N.
Заглавие : Crystal Structure of Three Ionic Compounds of Levofloxacin
Место публикации : J. Struct. Chem. - 2019. - Vol. 60, Is. 12. - P.1959-1964. - ISSN 00224766 (ISSN), DOI 10.1134/S0022476619120114
Примечания : Cited References: 13. - The work was performed within the State Task of the Ministry of Education and Science of the Russian Federation to the Siberian Federal University for 2017-2019 (4.7666.2017/BCh)
Аннотация: The structures of three ionic compounds of levofloxacin (LevoH or Ci18H20FN3O4) − LevoH3[CoCl4]-H2O (I), LevoH3[ZnBr4]·H2O (II), LevoH3[CuBr4]-H2O·(III) are determined. The crystals of I-III are monoclinic; in compound III, the particles are packed so that the direction of the screw axis does not coincide with the largest unit cell parameter. The asymmetric unit of the unit cell contains two LevoH32+ and CoCl42− ions and two crystallization water molecules in I; two LevoH32+ and MBr42− (M = Cu, Zn) ions and two crystallization water molecules in II and III. The absolute structure of the crystals and the configuration of the chiral center of the levofloxacinium cation S are determined. The structures are stabilized by multiple hydrogen bonds, X−Y π and π-π interactions.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vasil'ev A. D., Golovnev N. N., Lesnikov M. K.
Заглавие : Crystal structure of [Bi(N-ethylthiourea)4(ClO4)2]ClO4
Место публикации : Russ. J. Inorg. Chem.: MAIK Nauka-Interperiodica / Springer, 2016. - Vol. 61, Is. 6. - P.704-707. - ISSN 00360236 (ISSN), DOI 10.1134/S003602361606022X
Примечания : Cited References: 21
Ключевые слова (''Своб.индексиров.''): hydrogen bonds--bismuth complexes--mutual repulsion--octahedral cation--thiocarbonyl--crystal structure
Аннотация: The structure of the bismuth(III) complex with N-ethylthiourea (Ettu) has been determined for the first time. We found that the crystal structure of [Bi(Ettu)4(ClO4)2]ClO4 is built of distorted octahedral cations [Bi(Ettu–S)4(ClO4)2]ClO4]+ and anions ClO4 -. The deviation of one of the two independent Ettu molecules from the plane structure is explained by the mutual repulsion of the ligands and the formation features of hydrogen bonds. The C2H5(Ettu) group is in the cis position relative to the thiocarbonyl group. © 2016, Pleiades Publishing, Ltd.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Xia Z., Liu G., Wen J., Mei Z., Balasubramanian M., Molokeev M. S., Peng L., Gu L., Miller D. J., Liu Q., Poeppelmeier K. R.
Заглавие : Tuning of photoluminescence by cation nanosegregation in the (CaMg)x(NaSc)1-xSi2O6 solid solution
Место публикации : J. Am. Chem. Soc.: American Chemical Society, 2016. - Vol. 138, Is. 4. - P.1158-1161. - ISSN 00027863 (ISSN), DOI 10.1021/jacs.5b12788
Примечания : Cited References: 23. - Work performed by Z.X. and Q.L. was supported by the National Natural Science Foundation of China (51272242 and 51572023), the Program for New Century Excellent Talents in the University of the Ministry of Education of China (NCET-12-0950), and the Beijing Nova Program (Z131103000413047). Work performed by G.L., J.W., Z.M., M.B., and D.J.M. at Argonne National Laboratory was supported by the Office of Basic Energy Sciences of the U.S. Department of Energy (DOE) through Grant DE-AC02-06CH11357 for research on heavy elements chemistry and materials sciences. TEM was accomplished in part at the Center for Nanoscale Materials, a DOE Office of Science User Facility under Contract DE-AC02-06CH11357. Sector 20 operations at APS are supported by DOE and the Canadian Light Source, with additional support from the University of Washington. G.L. acknowledges travel support from the CAS/SAFEA International Partnership Program for Creative Research Teams. K.R.P. gratefully acknowledges support from the National Science Foundation (DMR-1307698).
Предметные рубрики: SPINODAL DECOMPOSITION
ENERGY-TRANSFER
EXSOLUTION
CLINOPYROXEN
NANOCRYSTALS
SEGREGATION
MECHANISMS
PYROXENESS
JERVISITE
PHOSPHORS
Аннотация: Controlled photoluminescence tuning is important for the optimization and modification of phosphor materials. Herein we report an isostructural solid solution of (CaMg)x(NaSc)1-xSi2O6 (0 < x < 1) in which cation nanosegregation leads to the presence of two dilute Eu2+ centers. The distinct nanodomains of isostructural (CaMg)Si2O6 and (NaSc)Si2O6 contain a proportional number of Eu2+ ions with unique, independent spectroscopic signatures. Density functional theory calculations provided a theoretical understanding of the nanosegregation and indicated that the homogeneous solid solution is energetically unstable. It is shown that nanosegregation allows predictive control of color rendering and therefore provides a new method of phosphor development. © 2016 American Chemical Society.
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13.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Sofronova S. N., Pavlovsky M. S., Chernyshov A. V., Moshkina E. M., Velikanov D. A.
Заглавие : Theoretical study of the cation and magnetic ordering in NixCo3-xB2O6
Коллективы : International Baltic Conference on Magnetism, Балтийский федеральный университет им. И. Канта
Место публикации : V International Baltic Conference on Magnetism. IBCM: Book of abstracts. - 2023. - P.191
Примечания : Cited References: 3. - РФФИ № 23-12-20012
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kazak N. V., Bayukov O. A., Ovchinnikov S. G., Vasiliev A. D., Rudenko V. V., Ivanova N. B., Knyazev Yu. V., Bartolom J., Arauzo A.
Заглавие : The superexchange interactions in mixed Co-Fe ludwigite
Место публикации : J. Magn. Magn. Mater. - 2011. - Vol. 323, Is. 5. - P.521-527. - MAR. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2010.09.057
Примечания : Cited Reference Count: 15. - Гранты: This study was supported by the Russian Foundation for Basic Research (Project no. 09-02-00171-a), the Federal Agency for Science and Innovation (Rosnauka) (Project no. MK-5632. 2010.2), Physical Division of the Russian Academy of Science, the program "Strongly Correlated Electrons", project 2.3.1.; The financial support of Spanish MINCYT, MAT08/1077 and Aragonese E-34 project are also acknowledged.Финансирующая организация: Russian Foundation for Basic Research [09-02-00171-a]; Federal Agency for Science and Innovation (Rosnauka) [MK-5632. 2010.2]; Physical Division of the Russian Academy of Science; "Strongly Correlated Electrons" [2.3.1]; Spanish MINCYT [MAT08/1077]; Aragonese E-34 project
Предметные рубрики: TRANSPORT-PROPERTIES
SPECTRA
Ключевые слова (''Своб.индексиров.''): ludwigite structure--magnetic susceptibility--magnetic frustration--mott conductivity--ludwigite structure--magnetic frustration--magnetic susceptibility--mott conductivity--ac susceptibility--cation distributions--crystal data--crystallographic sites--electrical resistivity--iron atoms--low temperatures--ludwigite structure--magnetic behavior--magnetic frustrations--magnetic system--magnetic transitions--mossbauer--mossbauer effects--mott conductivity--mott hopping--superexchange energy--superexchange interaction--temperature regions--trivalent iron--variable range--cobalt--electric conductivity--magnetic susceptibility--magnetism--mossbauer spectroscopy--x ray diffraction--crystal structure
Аннотация: The crystal structure, cation distribution and exchange interactions in the Co2.25Fe0.75O2BO3 ludwigite have been explored through X-ray diffraction, electrical resistivity, ac-susceptibility and Mossbauer effect measurements. The crystal data have shown that iron atoms occupy the most symmetric crystallographic sites Fe4 and Fe2. The complex magnetic behavior with two magnetic transitions near 70 and 115 K at low temperatures was found. The Mossbauer data have displayed the trivalent iron states only. The values of superexchange energies have been estimated for Co3O2BO3 and Co2.25Fe0.75O2BO3 yielding a significant role of frustrations in the ludwigite magnetic system. Variable range Mott hopping conductivity law was proved to be valid in the wide temperature region, pointing out a localized character of charge carriers rather than collective. (C) 2010 Elsevier B.V. All rights reserved.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sofronova S. N., Bezmaternykh L. N., Eremin E. V., Nazarenko I. I., Volkov N. V., Kartashev A. V., Moshkina E. M.
Заглавие : The superexchange interactions and magnetic ordering in low-dimentional ludwigite Ni5GeB2O10
Место публикации : J. Magn. Magn. Mater.: Elsevier, 2016. - Vol. 401. - P.217-222. - ISSN 0304-8853, DOI 10.1016/j.jmmm.2015.10.024
Примечания : Cited References: 23. - This study was supported by Russian Foundation for Basic Research (RFFI Siberia No. 15-42-04186). We thank S. Popkov, G. Yurkin for help on the magnetic measurements and M.S. Molokeev for help on the x-ray diffraction
Предметные рубрики: DIELECTRICS
EXCHANGE
CATION
Ключевые слова (''Своб.индексиров.''): ludwigites--magnetic order--heat capacity--exchange interactions--ferrimagnetic
Аннотация: The ludwigite Ni5Ge(BO5)2 belongs to a family of oxyborates which have low-dimensional subunits in the form of three-leg ladders unit structure. This material was studied by magnetic and thermodynamic measurements. Ni5Ge(BO5)2 does not show full long-range magnetic order, but one goes into a partial ordering or spin-glass state at 87 K. The superexchange interactions were calculated in the framework of a simple indirect coupling model. Different models of magnetic structure of Ni5Ge(BO5)2 and its unique magnetic behaviour was discussed. © 2015 Elsevier B.V.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gai S., Zhu H., Gao P., Zhou C., Kong Z., Molokeev M. S., Qi Z., Zhou Z., Xia M.
Заглавие : Structure analysis, tuning photoluminescence and enhancing thermal stability on Mn4+-doped La2-xYxMgTiO6 red phosphor for agricultural lighting
Место публикации : Ceram. Int. - 2020. - Vol. 46, Is. 12. - P.20173-20182. - ISSN 02728842 (ISSN), DOI 10.1016/j.ceramint.2020.05.095
Примечания : Cited References: 40. - The authors would like to gratefully acknowledge funds from the National Natural Science Foundation of China (Grant No. 21706060 , 51703061 , 51974123 ), the Hunan Graduate Research and Innovation Project (Grant No. CX2018B396 ), the Hunan provincial Engineering Technology Research Center for Optical Agriculture (Grant No. 2018TP2003 ), the Scientific Research Fund of Hunan Provincial Education Department (15K058, 19C0903), the Natural Sciences Foundation of Hunan agricultural university, China (Grant No. 19QN11), the Science and Technology project of Changsha (KH1801219) and the Huxiang high level talent gathering project (2019RS1077)
Аннотация: Currently, phosphor-converted LEDs (pc-LEDs) are revolutionizing the industry of plant growth lighting. To meet the requirements of this technology, phosphors with tunable photoluminescence, high thermal stability and luminous intensity are required. Herein, we found that the simple substitution of yttrium for lanthanum in La2MgTiO6:Mn4+ (LMT:Mn4+) system could satisfy above three criteria simultaneously. The photoluminescence properties can be regulated by continuously controlling the chemical composition of La2-xYxMgTiO6:Mn4+ solid solution. The La sites are occupied by Y ions, causing a significant blue shift in the emission spectra which owing to the change of local crystal field strengthen. Meanwhile, the thermal stability and decay lifetimes are also varied due to the variation of local structure and band gap energy. The thermal stability of the material reaches 83.5% at 150 °C, which is better than the reported La2MgTiO6:Mn4+ and Y2MgTiO6:Mn4+ phosphors. The electronic luminescence (EL) of pc-LED devices using La2-xYxMgTiO6:Mn4+ red phosphor is evaluated, which matching the absorption regions of plant pigments well, reflecting the superiority of the studied phosphors in plant growth lighting areas.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Wei Y., Lin C. C., Quan Z., Molokeev M. S., Atuchin V. V., Chan T. -S., Liang Y., Lin J., Li G.
Заглавие : Structural evolution induced preferential occupancy of designated cation sites by Eu2+ in M5(Si3O9)2 (M = Sr, Ba, Y, Mn) phosphors
Место публикации : RSC Adv.: Royal Society of Chemistry, 2016. - Vol. 6, Is. 62. - P.57261-57265. - ISSN 20462069 (ISSN), DOI 10.1039/c6ra11681g
Примечания : Cited References: 28. - This project is financially supported by the National Natural Science Foundation of China (Grants No. NSFC 21301162, 21571162, 60977013, 91433110, U1301242, 21221061), the National College Students' Innovative Training Program (Nos. 201510491109, 201610491067, 201610491070), and the Ministry of Science and Technology of Taiwan (No. MOST 104-2917-1-564-060). Zewei Quan acknowledges the funding support (FRG-SUSTC1501A-17) from South University of Science and Technology of China.
Предметные рубрики: LUMINESCENCE PROPERTIES
RED LUMINESCENCE
UP-CONVERSION
WHITE LEDS
PHOTOLUMINESCENCE
NANOPHOSPHORS
YELLOW
WLEDS
Аннотация: In this paper, we present new insight into a changing Eu2+ crystallographic site preference in Eu-doped M5(Si3O9)2 (M = Sr, Ba, Y, Mn), which is related to the structural variation induced by M cation substitutions. The effect of the local structural geometry on the luminescence properties of Eu2+ is revealed. By substitution of Ba2+ for Sr2+, the lattice expansion is restricted to specific cation sites, resulting in the abrupt blue shifted emission of Eu2+ ions. The abnormal blue shift on replacing Sr2+ with Mn2+ is attributed to the preferential 6-fold coordination for Mn2+ that moves the Eu2+ ions to other sites. The results elucidate the mechanisms of emission band adjustment by local site coordination change and it can be potentially extended to crystals which properties are sensitive to local lattice variations. © 2016 The Royal Society of Chemistry.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fang M. -H., Mahlik S., Lazarowska A., Grinberg M., Molokeev M. S., Sheu H. -S., Lee J. -F., Liu R. -S.
Заглавие : Structural Evolution and Effect of the Neighboring Cation on the Photoluminescence of Sr(LiAl3)1−x(SiMg3)xN4:Eu2+ Phosphors
Место публикации : Angew. Chem. Int. Ed. - 2019. - Vol. 58, Is. 23. - P.7767-7772. - ISSN 14337851 (ISSN), DOI 10.1002/anie.201903178
Примечания : Cited References: 23. - This work was supported by the Ministry of Science and Technology of Taiwan (Contract Nos. MOST 107‐2113‐M‐002‐008‐MY3 and MOST 107–2923‐M‐002‐004‐MY3). This work was supported by the National Science Centre Poland grant Opus no. 2016/23/B/ST3/03911 and the National Centre for Research and Development Poland Grant (No. PL‐TW/V/1/2018).
Предметные рубрики: Solid-Solution Phosphors
Аннотация: In this study, a series of Sr(LiAl3)1−x(SiMg3)xN4:Eu2+ (SLA‐SSM) phosphors were synthesized by a solid‐solution process. The emission peak maxima of SLA‐SSM range from 615 nm to 680 nm, which indicates structural differences in these materials. 7Li solid‐state NMR spectroscopy was utilized to distinguish between the Li(1)N4 and Li(2)N4 tetrahedra in SLA‐SSM. Differences in the coordination environments of the two Sr sites were found which explain the unexpected luminescent properties. Three discernible morphologies were detected by scanning electron microscopy. Temperature‐dependent photoluminescence and decay times were used to understand the diverse environments of europium ions in the two strontium sites Sr1 and Sr2, which also support the NMR analysis. Moreover, X‐ray absorption near‐edge structure studies reveal that the Eu2+ concentration in SLA‐SSM is much higher than that in in SrLiAl3N4:Eu2+ and SrSiMg3N4:Eu2+ phosphors. Finally, an overall mechanism was proposed to explain the how the change in photoluminescence is controlled by the size of the coordinated cation.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Li O. A., Lin C. -R., Chen H. -Y., Hsu, Hua-Shu, Shih K. -Y., Edelman I. S., Wu K. -W., Tseng Y. -T., Ovchinnikov S. G., Lee J. -S.
Заглавие : Size dependent magnetic and magneto-optical properties of Ni0.2Zn0.8Fe2O4 nanoparticles
Место публикации : J. Magn. Magn. Mater.: Elsevier, 2016. - Vol. 408. - P.206-212. - ISSN 03048853 (ISSN), DOI 10.1016/j.jmmm.2016.02.062
Примечания : Cited References: 51. - This work is supported by the Ministry of Science and Technology of Taiwan (MOST 103-2811-M-153 -001 and MOST 102-2112-M-153 -002 -MY3), and by the Russian Foundation for Basic Researches, grant No 14-02-01211.
Предметные рубрики: Zinc ferrite
Cation distribution
Sol-gel
Ni
ZnFe2O4
Spinel
Fe3O4
Particles
Spectra
State
Ключевые слова (''Своб.индексиров.''): nickel zinc ferrite--nanoparticles--magnetic properties--mcd
Аннотация: Ni0.2Zn0.8Fe2O4 spinel nanoparticles have been synthesized by combustion method. Average particles size varies from 15.5 to 50.0 nm depending on annealing temperature. Correlations between particles size and magnetic and magneto-optical properties are investigated. Magnetization dependences on temperature and external magnetic field correspond to the sum of paramagnetic and superparamagnetic response. Critical size of single-domain transition is found to be 15.9 nm. Magnetic circular dichroism (MCD) studies of nickel zinc spinel are presented here for the first time. The features in magnetic circular dichroism spectrum are assigned to the one-ion d-d transitions in Fe3+ and Ni2+ ions, as well to the intersublattice and intervalence charge transfer transitions. The MCD spectrum rearrangement was revealed with the change of the nanoparticles size. © 2016 Elsevier B.V. All rights reserved.
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20.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Ryabinkina L. I., Romanova O. B., Kisilev N. I.
Заглавие : Magnetotranport properties of cation-substituted sulphides VXMn1-XS
Коллективы : Moscow International Symposium on Magnetism, Московский государственный университет им. М.В. Ломоносова
Место публикации : Moscow Int. Symp. on Magnet. (MISM-2014): Book of abstracts. - 2014. - Ст.1PO-K-11. - P.544. - ISBN 978-5-91978-025-0
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