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1.

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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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mikhaleva E. A., Flerov I. N., Gorev M. V., Molokeev M. S., Cherepakhin A. V., Kartashev A. V., Mikhashenok N. V., Sablina K. A.
Заглавие : Caloric characteristics of PbTiO3 in the temperature range of the ferroelectric phase transition
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2012. - Vol. 54, Is. 9. - P.1832-1840. - ISSN 1063-7834, DOI 10.1134/S1063783412090181
Примечания : Cited References: 31. - This study was supported by the Russian Foundation for Basic Research (project no. 12-08-00079) and the Council on Grants from the President of the Russian Federation for Support of Leading Scientific Schools of the Russian Federation (grant no. NSh-4828.2012.2).
Предметные рубрики: SINGLE-CRYSTALS
LEAD TITANATE
DIELECTRIC PROPERTIES
SOLID-SOLUTIONS
PRESSURE
PEROVSKITES
DEPENDENCE
BEHAVIOR
HEAT
Аннотация: The heat capacity and thermal expansion of the PbTiO3 ceramic sample have been measured in the temperature range 80–970 K. The electrocaloric and barocaloric efficiencies of lead titanate in the ferroelectric phase transition range have been investigated by analyzing the experimental data in terms of the thermodynamic theory of phase transitions, the electrical equation of state P(T, E), the Pippard equation, and the S(T, p) diagram.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Edelman I. S., Greben'kova Yu. E., Sokolov A. E., Molokeev M. S., Aleksandrovsky A. S., Chichkov V. I., Andreev N. V., Mukovskii Y.
Заглавие : Visible magnetic circular dichroism spectroscopy of the Pr0.8Sr0.2MnO3 and Pr0.6Sr0.4MnO3 thin films
Место публикации : AIP Adv.: American Institute of Physics, 2014. - Vol. 4, Is. 5. - Ст.057125. - ISSN 2158-3226, DOI 10.1063/1.4879818
Примечания : Cited References: 30. - The work was supported partly by the Russian Foundation for Basic Researches, grant No’s 14-02-01211, 12-02-00717-a and Grant of the Russian President No Sh-2886.2014.2
Предметные рубрики: MANGANITES
LA1-XSRXMNO3
PEROVSKITES
SPECTRA
Аннотация: Visiblemagnetic circular dichroism (MCD) in Pr1-xSrxMnO3 with x=0.2 and 0.4was investigated for the first time. Samples for the investigation – polycrystalline films with thickness from 20 to 150 nm were prepared with the dc magnetron sputtering. MCD spectra obtained in the energy interval 1–4 eV at temperatures 100–300 K consist of several maxima with different intensities: very strong one near 3.25–3.4 eV and a broad essentially weaker band near 2 eV. An additional maximum of opposite sign arises in the samples with x = 0.4MCD spectrum at 2.33 eV. Experimental spectra were decomposed to several Gaussian components, and their amplitudes temperature dependences were analyzed. In the case of x = 0.2, all four Gaussian components are characterized by the identical temperature dependence of their amplitudes. In the case of x = 0.4, maxima observed in different spectral intervals demonstrate different temperature dependences of their amplitudes. One more unexpected phenomenon is associated with the different MCD value change in different spectral intervals when coming from x = 0.2 to x = 0.4: high-energy maximum increases more than twice while low-energy maxima intensity stays at that, practically, unchanged.
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zinenko V. I., Zamkova N. G., Zhandun V. S., Pavlovskii M. S.
Заглавие : Ferroelectric and structural instability in double perovskites Me1+Bi3+Me3+Nb5+O6 (Me1+ = Na, K, Rb; Me3+ = Sc, Ga, In, Lu)
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2012. - Vol. 114, Is. 6. - P.955-962. - ISSN 1063-7761, DOI 10.1134/S1063776112040188
Примечания : Cited References: 7. - This work was supported by the Russian Foundation for Basic Research (project no. 09-02-00067) and by the program for the support of leading scientific schools (project no. NSh-4645.2010.2).
Аннотация: Within the Gordon-Kim generalized model with regard to the polarizabilities of ions, the lattice constants, the high-frequency permittivity, the Born dynamic charges, and the vibration constants of the crystal lattice are calculated for cation-ordered double perovskites Me1+Bi3+Me3+Nb5+O6. The vibration spectra of all the compounds exhibit two types of instabilities: instability associated with the rotation of the oxygen octahedron and ferroelectric instability. Various combinations of distortions with respect to the rotation mode yield five energetically most favorable distorted phases. The symmetry and the energy characteristics of these phases are discussed. In four of the five phases, the distortions associated with the oxygen octahedron rotation lead to polar phases, thus allowing one to speak of improper ferroelectricity in these compounds. One phase turns out to be nonpolar; however, it contains unstable polar modes such that a displacement along the eigenvectors of these modes gives rise to polarization in the crystal.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Vereshchagin S. N., Solovyov L. A., Rabchevskii E. V., Dudnikov V. A., Ovchinnikov S. G., Anshits A. G.
Заглавие : Methane oxidation over A-site ordered and disordered Sr0.8Gd0.2CoO3−δ perovskites
Коллективы : SB RAS project [38]; RFBR [13-02-00358]
Место публикации : Chem. Commun.: Royal Society of Chemistry, 2014. - Vol. 50, Is. 46. - P.6112-6115. - ISSN 1359-7345, DOI 10.1039/c4cc00913d. - ISSN 1364-548X
Примечания : Cited References: 20. - The authors acknowledge the financial support from SB RAS project N 38 (2012) and RFBR grant 13-02-00358.
Предметные рубрики: MEMBRANE REACTORS
OXYGEN
OXIDES
PERFORMANCE
COMBUSTION
FEATURES
PHASES
Аннотация: A tetragonal phase Sr0.8Gd0.2CoO3−δ with ordered Gd3+/Sr2+ ions and oxygen vacancy sites is found to be about five times less active in the reaction of methane combustion than a quenched cubic perovskite phase with randomly distributed (disordered) Gd3+/Sr2+ ions over the A-sites of the crystal lattice.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Aleksandrov K. S., Tressaud A., Fokina V. D.
Заглавие : Ferroelastic phase transitions in fluorides with cryolite and elpasolite structures
Место публикации : Crystallogr. Rep. - 2004. - Vol. 49, Is. 1. - P.100-107. - ISSN 1063-7745, DOI 10.1134/1.1643969
Примечания : Cited References: 43
Предметные рубрики: NUCLEAR MAGNETIC-RESONANCE
THERMODYNAMIC PROPERTIES
RB2KMIIIF6 ELPASOLITES
NEUTRON-DIFFRACTION
CRYSTALS
PEROVSKITES
DIAGRAM
SC
RB2KGAXSC1-XF6
SCATTERING
Аннотация: The ferroelastic phase transitions are investigated in several series of fluoride crystals belonging to the elpasolite and cryolite families (space group Fm (3) over barm) with the general formula A(2)BB'F-6. The influence of the size and shape of cations and anions on the entropy and the mechanism of structural distortions is discussed. (C) 2004 MAIK "Nauka/Interperiodica".
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S., Bartolome J.
Заглавие : Structural distortions in families of perovskite-like crystals
Место публикации : Phase Transit.: TAYLOR & FRANCIS LTD, 2001. - Vol. 74, Is. 3. - P.255-335. - ISSN 0141-1594, DOI 10.1080/01411590108228754
Примечания : Cited References: 262
Предметные рубрики: LOW-TEMPERATURE PHASE
INELASTIC-NEUTRON-SCATTERING
POWDER PROFILE REFINEMENT
MII = CO
X-RAY
RAMAN-SCATTERING
ORDERED PEROVSKITE
RHOMBOHEDRAL PEROVSKITES
RB2KMIIIF6 ELPASOLITES
MAGNETIC-PROPERTIES
Ключевые слова (''Своб.индексиров.''): structural phase transitions--perovskites--perovskite-like crystals--group theoretical classification
Аннотация: The crystallographic and group theoretical analysis of the structural phase transitions in perovskite and perovskite-like crystals is reviewed. We include ABX(3) perovskites and their relative crystals of ReO3 type (G(0) = O-h(1)), elpasolites, cryolites and their relatives (G(0) = O-h(5)) layered crystals of TIAIF(4) series (G(0) = D-4h(1)), Aurivillius and Ruddlesden-Popper series (G(0) = D-4h(17)). The structures in their initial phase G(0) often contain n layers (n = 1, 2,3) of vertex linked octahedra. The distorted phases produced by one kind of tilt and by superposition of tilts in the slabs are enumerated. Most of the tilts correspond to symmetry changes, which can be associated to definite librational lattice modes irreducible representations of the G(0) group. The softening of modes associated to the PT has been found experimentally in many perovskites, elpasolites and layered crystals with n = 1. In contrast, no such soft modes have been found yet for even-layered (n = 2) crystals. Examples of successive phase transitions due to the superposition of tilts in these types of crystals have been collected.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S., Bartolome J., Gorev M. V., Flerov I. N.
Заглавие : Hydrostatic pressure effect on phase transitions in perovskites with ammonium cations
Место публикации : Phys. Status Solidi B. - 2000. - Vol. 217, Is. 2. - P.785-791. - ISSN 0370-1972, DOI 10.1002/(SICI)1521-3951(200002)217:2785::AID-PSSB7853.0.CO;2-Y
Примечания : Cited References: 36
Предметные рубрики: XMF3 CUBIC PEROVSKITES
THERMAL-PROPERTIES
HEAT-CAPACITY
TEMPERATURE DEPENDENCE
DIELECTRIC PROPERTIES
X-RAY
NH4ZNF3
NH4MNCL3
NH4COF3
NH4CDF3
Аннотация: The pressure dependence of the structural phase transition temperature has been measured for the powder samples of NH4MgF3, NH4ZnF3, NH4MnF3, NH4CoF3, NH4CdF3, and NH4MnCl3 perovskites in the pressure range 0 to 600 MPa. It was found that the values of dT(0)/dP are negative for the Mg, Zn. Co. Mn trifluorides and positive for NH4CdF3 and NH4MnCl3. Comparison with the known data for other halide and oxide perovskites allowed to conclude that the sign of dT(0)/dP is correlated with the value of the Goldschmidt tolerance factor of the perovskite, and its value is closely related to the temperature and mechanism of the transition.
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S., Beznosikov B. V.
Заглавие : Architecture and properties of perovskite-like crystals
Коллективы : USA-CIS-Baltic Seminar on Ferroelectricity
Место публикации : Ferroelectrics: Gordon Breach Sci Publ Ltd, 1999. - Vol. 226, Is. 1-4. - P.1-9. - ISSN 0015-0193, DOI 10.1080/00150199908230285
Примечания : Cited References: 9
Ключевые слова (''Своб.индексиров.''): perovskites--perovskite-like crystals--new representatives of ruddlesden-popper's phases--new representatives of ruddlesden-popper's phases--perovskite-like crystals--perovskites
Аннотация: A variety of the known structures of perovskite-like crystals including cation- and anion-deficient phases were considered as the intergrowth systems of slabs containing n-layers (n = 1,2, 3,...infinity) of corner-linked octahedra BX6, pyramids EX5 or square-planar nets BX4 (B-cation, X- anion) linked by intermediate blocks of different types.([1- 3]) Some new structural types and new representatives of ferroelectrics, ferroelastics and HTSC's can be constructed on this basis. The prognosis of new possible representatives in Ruddlesden-Popper's family is discussed.A variety of the known structures of perovskite-like crystals including cation- and anion-deficient phases were considered as the intergrowth systems of slabs containing n-layers (n = 1, 2, 3, . . . ?) of corner-linked octahedra BX6, pyramids BX5 or square-planar nets BX4 (B-cation, X-anion) linked by intermediate blocks of different types.[1-3] Some new structural types and new representatives of ferroelectrics, ferroelastics and HTSC's can be constructed on this basis. The prognosis of new possible representatives in Ruddlesden-Popper's family is discussed.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Melnikova S. V., Anistratov A. T., Aleksandrov K. S.
Заглавие : Birefringes and structure phase-transitions in ABCl3 perovskites
Место публикации : Fiz. Tverd. Tela: Mezhdunarodnaya kniga, 1981. - Vol. 23, Is. 1. - P.246-250. - ISSN 0367-3294
Примечания : Cited References: 16
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Aleksandrov K. S., Tressaud A., Grannec J., Couzi M.
Заглавие : Phase transitions in elpasolites (ordered perovskites)
Место публикации : Materials Science and Engineering R: Reports. - 1998. - Vol. 24, Is. 3. - P.81-151. - ISSN 0927-796X
Примечания : Cited References: 174
Предметные рубрики: ELASTIC NEUTRON-DIFFRACTION
MII = CO
RAMAN-SCATTERING
THERMODYNAMIC PROPERTIES
CRYSTAL-STRUCTURE
SINGLE-CRYSTALS
RB2KMIIIF6 ELPASOLITES
CUBIC PEROVSKITES
TEMPERATURE FORM
HIGH-RESOLUTION
Ключевые слова (''Своб.индексиров.''): crystal atomic structure--crystal growth--crystal lattices--crystallization--crystallography--ferroelectricity--hydrostatic pressure--order disorder transitions--single crystals--thermodynamics--elpasolites--landau theory--perovskite
Аннотация: Many compounds with general chemical formula A2BB?X6 and with tolerance factor value t < 1 crystallize in the elpasolite (ordered perovskite) structure. Different preparative methods have been considered. For example, the Bridgman technique is the most suitable method of growing single crystals of halogenated elpasolites with monoatomic cations. Group-theory and symmetry analyses have allowed us to build a scheme of possible structural distortions connected with octahedral rotations and displacements of ions. Experimental observations have proven that ferroelastic phase transitions occurring most frequently in elpasolites are due to small octahedra tilts. Quantitative analysis allows the possibility of describing these transitions in the framework of the thermodynamic Landau theory. Hydrostatic pressure and the substitution of atoms in different crystallographic sites allow to change significantly the succession and the temperature of phase transitions. The hypothesis of bond stresses is able to predict the possible occurrence of a phase transition for a particular elpasolite and/or the role of the octahedra rotations in the transformation. The mechanism of phase transitions in elpasolites and related compounds has also been considered. One can assume that a displacive mechanism associated with a strong anharmonicity plays a large role in phase transitions occurring in compounds with monoatomic cations. On the other hand, for instance, in cryolites with ammonium cations, the transitions originate from an order-disorder phenomenon. В© 1998 Elsevier Science S.A. All rights reserved.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhandun V. S., Zamkova N. G., Zinenko V. I.
Заглавие : Effect of an Eu3+ impurity on the antiferrodistortion and ferroelectric instabilities in an EuTiO3 bulk crystal and thin films
Коллективы : Russian Foundation for Basic Research [12-02-00025-a], Russian Federation [NSh-924.2014.2]
Место публикации : J. Exp. Theor. Phys.: MAIK Nauka-Interperiodica / Springer, 2015. - Vol. 120, Is. 1. - P.103-109. - ISSN 1063, DOI 10.1134/S1063776115010070. - ISSN 10906509(eISSN)
Примечания : Cited References:21. - This work was supported by the Russian Foundation for Basic Research (project no. 12-02-00025-a) and the program Leading Scientific Schools of the President of the Russian Federation (project no. NSh-924.2014.2).
Предметные рубрики: PEROVSKITES
Аннотация: The existence of an antiferrodistortion transition in EuTiO3 is disputable, and this question needs to be answered. One of the possible causes is the presence of an Eu3+ impurity in a sample. A nonempirical polarizable ion model is used to study the effect of a trivalent Eu3+ ion impurity on the antiferrodistortion and ferroelectric instabilities of an EuTiO3 crystal in the bulk and the thin-film states. Lattice dynamics calculation shows that a bulk impurity-free EuTiO3 crystal has no unstable modes throughout the entire phase space volume. The addition of an Eu3+ impurity leads to a significant softening of the rotational mode, the distortion in which makes tetragonal phase I4/mcm (which is experimentally observed) energetically favorable. In going from the bulk crystal to the thin film, the vibration spectrum of the impurity-free film has unstable antiferrodistortion and rotational modes. The addition of an Eu3+ impurity enhances the antiferrodistortion instability, which fully or partly suppresses ferroelectricity.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhandun V. S., Zinenko V. I.
Заглавие : Ab initio investigation of the magnetic and ferroelectric properties of double perovskites LaPbMeSbO6 (Me = Mn, Fe, Co, Ni)
Коллективы : Russian Foundation for Basic Research [12-02-00025-a], Russian Federation [NSh-924-2014.2]
Место публикации : Phys. Solid State: MAIK Nauka-Interperiodica / Springer, 2015. - Vol. 57, Is. 5. - P.983-991. - ISSN 1063, DOI 10.1134/S1063783415050340. - ISSN 10906460(eISSN)
Примечания : Cited References:19. - This study was supported by the Russian Foundation for Basic Research (project no. 12-02-00025-a) and the Council on Grants from the President of the Russian Federation in Support of the Leading Scientific Schools (grant no. NSh-924-2014.2). Calculations were performed on supercomputers of the National Research Centre "Kurchatov Institute" (Moscow, Russia).
Аннотация: The results of ab initio calculations of the ferroelectric and magnetic properties of the recently synthesized double perovskites LaPbMeSbO6 (Me (2+) = Mn2+, Fe2+, Co2+, Ni2+) have been presented. The ordered double perovskites with a layered ordering of cations A and A' and a checkerboard ordering of cations B and B' have been considered. The calculation of the lattice dynamics has revealed instabilities in the phonon spectra of the high-symmetry phase of these compounds. The condensation of unstable modes leads to a stable polar phase P2(1). The spontaneous polarization in this phase is found to be 30 mu C/cm(2). The magnetic ground state is antiferromagnetic with an antiparallel direction of the magnetic moments in adjacent planes along the [001] direction. The N,el temperatures are estimated in the mean field approximation. The presence of the ferroelectric and magnetic order parameters in the structure suggests that the studied double perovskites with the simultaneous ordering of the cations are potential multiferroics.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S.
Заглавие : The sequences of structural phase transitions in perovskites
Место публикации : Ferroelectrics. - 1976. - Vol. 14, Is. 1. - P.801-805. - DOI 10.1080/00150197608237799
Аннотация: A classification of the octahedral tilt systems in perovskites is given, based on the work of Glazer1 but extending it and using a new notation; this leads to a simple description of the sequences of phase transitions, and shows how they are related to the soft modes M3 and R25. Examples from the literature are discussed.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S., Beznosikov B. V., Posdnjakova L. A.
Заглавие : Successive phase transitions in perovskites. II. Structures of distorted phases
Коллективы : European meeting on ferroelectricity
Место публикации : Ferroelectrics. - 1976. - Vol. 12, Spesial issue. - P.197-198. - DOI 10.1080/00150197608241424
Аннотация: Estimation of atomic displacements from the unit cell distortions is discussed for the perovskites having successive structural phase transitions. The distorted structures of CsPbCl3 and CsSrCl3 are proposed.
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16.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Safonov I. N., Molokeev M. S., Misyul S. V., Sevrukov R. G.
Заглавие : Phenomenological Landau theory of the structural phase transitions in layered perovskites TlAlF4 type
Коллективы : International seminar on ferroelastic physics, Международный семинар по физике сегнетоэластиков, Российская академия наук, Воронежский государственный технический университет
Место публикации : The Eighth Int. Sem. on Ferroelastic Phys.: book of abstracts. - 2015. - P.20

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17.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Vereshchagin S. N., Solovyov L. A., Shishkina N. N., Dudnikov V. A., Anshits A. G.
Заглавие : Oxidative conversion of methane over Gd-Sr-Co-perovskites: structure-activity relationship
Коллективы : European Congress on Catalysis "Catalysis: Balancing the use of fossil and renewable resources”
Место публикации : 12th Eur. Congress on Catalysis (EuropaCat-XII): [proceedings]. - 2015
Примечания : Библиогр.: 4
Ключевые слова (''Своб.индексиров.''): methane--oxidation--ocm--perovskite --crystal structure
Материалы конгресса
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Sevryukov R. G., Safonov I. N., Molokeev M. S., Misyul S. V.
Заглавие : Phases of anionic ordering in elpasolite structures (Ordered perovskites)
Место публикации : J. Sib. Fed. Univ. Math. Phys. - 2016. - Vol. 9, Is. 1. - P.108-118. - ISSN 1997-1397, DOI 10.17516/1997-1397-2016-9-1-108-118; Журн. СФУ. Сер. "Математика и физика"
Примечания : Cited References: 20. - The research is conducted within the framework of the state task of Ministry of Education and Science of the Russian Federation to Siberian Federal University on R&D performance in 2015 (Task 3.2534.2015/K)
Ключевые слова (''Своб.индексиров.''): elpasolite--structural data--complete condensate of order parameters--irreducible representations--critical distortion--phase transition--dissymmetric phases--эльпасолит--структурные данные--полный конденсат параметров порядка--неприводимые представления--критические искажения--фазовый переход--диссимметричные фазы
Аннотация: The 108 dissymmetric phases were obtained as a result of X anions ordering in elpasolite structure A2BB′X6 (ordered perovskite) using group theoretical methods. The critical order parameters which transform according to the irreducible representations of Γ and X points of Brillouin zone of O5 h— F m3m space group were considered only. Polyhedral structures showed for dissymmetric phases which are ac- companied by appearing of ferroelectricity at phase transition. All results are summarized in convenient tables. © Siberian Federal University. All rights reserved.Теоретико-групповыми методами получено 108 диссимметричных фаз, возникающих в результате упорядочения анионов X в структуре эльпасолита A2BB ′ X6 (упорядоченного перовскита). Из критических параметров порядка рассмотрены только такие, которые преобразуют- ся по неприводимым представлениям точек Γ и X зоны Бриллюэна пространственной группы O5 h —F m3m. Для диссимметричных фаз, переходы в которые могут сопровождаться возникновением сегнетоэлектричества, приведены полиэдрические изображения структур. Все результаты собраны в удобных для использования таблицах.
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19.

Вид документа : Однотомное издание
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Molokeev M. S., Laptash N. M.
Заглавие : Ferroelastic and ferroelectric phase transitions in fluoro- and oxyfluorometallates
Место публикации : Photonic and electronic properties of fluoride materials: Elsevier, 2016. - Chapter 16. - P.355-381. - (Progress in fluorine science series). - , DOI 10.1016/B978-0-12-801639-8.00016-7
Примечания : Cited References: 92. - The reported study was partially supported by RFBR, research project No. 15-02-02009 a
Предметные рубрики: ELASTIC NEUTRON-DIFFRACTION
ORIENTATIONAL DISORDER
CRYSTAL-STRUCTURES
THERMODYNAMIC PROPERTIES
NONCRITICAL PARAMETERS
CUBIC PEROVSKITES
RAMAN-SCATTERING
SINGLE-CRYSTALS
A2BX4 STRUCTURE
HIGH-RESOLUTION
Аннотация: Different degree of structural disorder is one of the main features of many fluoro- and oxyfluorometallates crystallizing in high symmetry structures. The comprehensive study of these compounds (perovskites, elpasolites, pyrochlores, etc.) enabled to determine a great effect of the size and shape as well as crystallographic sites of cationic and anionic species on the mechanism of structural ordering. Ferroelastic and ferroelectric phase transitions of different order, type, and succession can be realized as a result of chemical and hydrostatic pressure change. It was found that the substitution of monoatomic cations for tetrahedral ammonium group was accompanied by rather significant change of electron density distribution, entropy, and phase diagrams. Some compounds studied were considered to be promising solid-state refrigerants owing to the pronounced barocaloric effect resulting from large entropy and baric coefficient of phase transitions.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhandun V. S., Zamkova N. G., Zinenko V. I.
Заглавие : Lattice dynamics and the ferroelectric phase transition in ordered Pb-2 B'BaEuro(3)O(6) (B' = Ga, In, Lu; BaEuro(3) = Nb, Ta) solid solutions
Коллективы :
Разночтения заглавия :авие SCOPUS: Lattice dynamics and the ferroelectric phase transition in ordered Pb2 B′ B″O6 (B′ = Ga, In, Lu; B″ = Nb, Ta) solid solutions
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2010. - Vol. 52, Is. 2. - P357-363. - ISSN 1063-7834, DOI 10.1134/S1063783410020228
Примечания : Cited References: 19. - This study is supported by the Russian Foundation for Basic Research (project no. 09-02-00067) and the Council on Grants from the President of the Russian Federation for Support of the Leading Scientific Schools (grant no. NSh-4137.2006.2).
Предметные рубрики: PEROVSKITES
CRYSTALS
DISORDER
RELAXOR
BATIO3
PBTIO3
Аннотация: The lattice vibration spectrum, rf permittivity, and dynamic Born charges have been calculated for ordered Pb-2 B'BaEuro(3)O(3) (B'=Ga, In, Lu; BaEuro(3)=Nb, Ta) solid solutions in terms of the generalized Gordon-Kim model. It has been shown that all compounds exhibit a ferroelectric instability and that the frequencies of "soft" ferroelectric modes are close in magnitude. The ferroelectric phase-transition temperatures and the spontaneous polarization in the ferroelectric phase of the solid solutions under consideration have been calculated by the Monte Carlo method using the model Hamiltonian in the local mode approximation. The transition temperature is found to increase with increasing atomic number of the B' ion.
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