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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zinenko V. I., Zamkova N. G.
Заглавие : Theory of an Fm3m - I4/m structural phase transition in an Rb2KScF6 crystal
Разночтения заглавия :us: Theory of an Fm3mI4/m Structural Phase Transition in an Rb2KScF6 Crystal
Место публикации : J. Exp. Theor. Phys.: AMER INST PHYSICS, 2000. - Vol. 91, Is. 2. - P314-323. - ISSN 1063-7761, DOI 10.1134/1.1311990
Примечания : Cited References: 16
Предметные рубрики: FIRST-PRINCIPLES THEORY
LATTICE-DYNAMICS
PEROVSKITES
ELPASOLITES
Аннотация: An Rb2KScF6 crystal having an elpasolite structure undergoes a sequence of Fm3m -- I4/m -- P12(1)/n1 structural phase transitions where the transition to the tetragonal phase is associated with "rotation" of the ScF6 octahedron. An effective Hamiltonian is constructed to describe the Fm3m -- I4/m transition using the approximation of a local mode for which we selected a "soft mode" whose eigenvector corresponds to the rotation of the octahedron. The effective Hamiltonian also includes the relationship between the local mode and the homogeneous elastic strains. The parameters of the effective Hamiltonian were determined using the generalized Gordon-Kim model of an ionic crystal which allows for the deformability and polarizability of the ions. The thermodynamic properties of a system with this model Hamiltonian were investigated using the Monte Carlo method. The calculated phase transition temperature of 250 K is almost the same as the experimental value (252 K). The tetragonal phase remains stable as far as T = 0 K and a second transition (to the monoclinic phase) cannot be obtained using this effective Hamiltonian. This suggests that if the transition to the tetragonal phase is mainly associated with "rotations" of the octahedrons, in order to describe the phase transition to the monoclinic phase the effective Hamiltonian must allow for additional degrees of freedom mainly associated with the motion of rubidium ions. (C) 2000 MAIK "Nauka/Interperiodica".
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M. V., Bondarev V. S., Flerov I. N., Maglione M., Simon A., Sciau P., Boulos M., Guillemet-Fritsch S.
Заглавие : Thermal expansion, polarization and phase diagrams of Ba1-yBi2y/3Ti1-xZrxO3 and Ba1-yLayTi1-y/4O3 compounds
Коллективы : Russian Foundation for Basic Research [07-02-00069]; Council on Grants from the President of the Russian Federation for Support of Leading Scientific Schools [NSh-1011.2008.2]
Разночтения заглавия :авие SCOPUS: Thermal expansion, polarization and phase diagrams of Ba 1-yBi2y/3Ti1-xZrxO3 and Ba1-yLayTi1-y/4O3 compounds
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2009. - Vol. 21, Is. 7. - Ст.75902. - С. P. - ISSN 0953-8984, DOI 10.1088/0953-8984/21/7/075902
Примечания : Cited References: 28. - This work was supported by the Russian Foundation for Basic Research ( project no. 07-02-00069) and the Council on Grants from the President of the Russian Federation for Support of Leading Scientific Schools ( project no. NSh-1011.2008.2).
Предметные рубрики: HEAT-CAPACITY
CERAMICS
BA(TI1-XZRX)O-3
FERROELECTRICS
BEHAVIOR
BATIO3
BATI0.65ZR0.35O3
CONDUCTIVITY
PEROVSKITES
CHEMISTRY
Ключевые слова (''Своб.индексиров.''): barium--dielectric properties--lanthanum--phase diagrams--polarization--thermal stress--zirconium--ceramic compositions--root mean squares--temperature ranges--temperature-dependent measurements--thermal expansion co-efficient--thermal-expansion properties--thermal expansion
Аннотация: The thermal expansion properties of the ceramic compositions Ba1-yLayTi1-y/4O3 (y = 0.0, 0.026, 0.036, 0.054) and Ba1-yBi2y/3Ti1-xZrxO3 (y = 0.10; x = 0.0, 0.04, 0.05, 0.10, 0.15) were determined in the temperature range 120-700 K. We report the temperature- dependent measurements of the strain, thermal expansion coefficient and the magnitude of root mean square polarization. The results obtained are discussed together with the data on the structure and dielectric properties.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zinenko V. I., Zamkova N. G.
Заглавие : Lattice dynamics and statistical mechanics of the Fm3m - I4/m structural phase transition in Rb2KInF6
Разночтения заглавия :авие SCOPUS: Lattice dynamics and statistical mechanics of the Fm3m I4/m structural phase transition in Rb2KInF6
Место публикации : Phys. Solid State: AMER INST PHYSICS, 2001. - Vol. 43, Is. 12. - P2290-2300. - ISSN 1063-7834, DOI 10.1134/1.1427959
Примечания : Cited References: 18
Предметные рубрики: FIRST-PRINCIPLES THEORY
RB2KSCF6 CRYSTAL
ELPASOLITES
PEROVSKITES
Аннотация: The static and dynamic properties of cubic Rb2KInF6 crystals with elpasolite structure are calculated using a nonempirical method. Calculations are performed within a microscopic ionic-crystal model taking into account the deformation and polarization of ions. The deformation parameters of ions are determined by minimizing the total energy of the crystal. The calculated equilibrium lattice parameters agree satisfactorily with the experimental data. It is found that in the cubic phase there are vibrational modes that are unstable everywhere in the Brillouin zone. The eigenvectors of the unstablest mode at the center of the Brillouin zone of the cubic phase are associated with the displacements of F ions and correspond to rotations of InF6 octahedra. Condensation of this mode leads to a tetragonal distortion of the structure. In order to describe the Fm3m -- I4/m phase transition, an effective Hamiltonian is constructed under the assumption that the soft mode whose eigenvector corresponds to octahedron rotation is local and coupled with homogeneous elastic strains. The parameters of the effective Hamiltonian are determined using the calculated crystal energy for the distorted structures due to soft-mode condensation. The thermodynamic properties of the system with this model Hamiltonian are investigated using the Monte Carlo method. The phase transition temperature is calculated to be 550 K, which is twice its experimental value (283 K). The tetragonal phase remains stable down to T = 0 K; the effective Hamiltonian used in this paper thus fails to describe the second phase transition (to the monoclinic phase). Thus, the transition to the tetragonal phase occurs for the most part through octahedron rotations; however, additional degrees of freedom, first of all, the displacements of Rb ions, should be included into the effective Hamiltonian in order to describe the transition to the monoclinic phase. (C) 2001 MAIK "Nauka/ Interperiodica".
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Zamkova N. G., Zinenko V. I.
Заглавие : Lattice dynamics and ferroelectric phase transitions in solid solutions PbSc(1/2)Nb(1/2)O(3) and PbSc(1/2)Ta(1/2)O(3)
Разночтения заглавия :авие SCOPUS: Lattice dynamics and ferroelectric phase transitions in solid solutions PbSc1/2Nb1/2O3 and PbSc1/2Ta 1/2O3
Место публикации : 12TH INTERNATIONAL CONFERENCE ON PHONON SCATTERING IN CONDENSED MATTER (PHONONS 2007). Ser. Journal of Physics Conference Series: IOP PUBLISHING LTD, 2007. - Vol. 92: 12th International Conference on Phonon Scattering in Condensed Matter (PHONONS 2004) (JUL 15-20, 2007, Paris, FRANCE). - Ст.12162. - ISBN 1742-6588, DOI 10.1088/1742-6596/92/1/012162
Примечания : Cited References: 14
Предметные рубрики: PEROVSKITES
BATIO3
Аннотация: The calculation of the lattice dynamics and ferroelectric phase transitions for disordered and ordered solid solution PbSc(1/2)Nb(1/2)O(3) and PbSC(1/2)Ta(1/2)O(3) in the framework of the Gordon-Kim model are performed. The unstable ferroelectric modes were found in all cases. The model Hamiltonian for the study finite temperature behavior during for the ferroelectric phase transition is used. The transition temperatures, phase sequences and spontaneous polarizations are calculated by Monte-Carlo method.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M. V., Flerov I. N., Bondarev V. S., Sciau P., Savariault J. M.
Заглавие : Heat capacity and thermal expansion study of relaxor-ferroelectric Ba0.92Ca0.08Ti0.76Zr0.24O3
Разночтения заглавия :авие SCOPUS: Heat capacity and thermal expansion study of relaxor-ferroelectric Ba 0.92Ca0.08Ti0.76Zr0.24O3
Место публикации : J. Phys.: Condens. Matter. - 2004. - Vol. 16, Is. 39. - P.7143-7150. - ISSN 0953-8984, DOI 10.1088/0953-8984/16/39/045
Примечания : Cited References: 18
Предметные рубрики: CERAMICS
BA(TI1-XZRX)O-3
PEROVSKITES
Ключевые слова (''Своб.индексиров.''): calorimetry--dielectric properties--ferroelectric materials--perovskite--phase transitions--solid solutions--specific heat--thermal expansion--adiabatic calorimetry--frequency dispersion--polar domains--relaxor ferroelectrics--barium compounds
Аннотация: Heat capacity and thermal expansion of the Ba0.92Ca0.08Ti0.76Zr0.24O3 compound is measured using the methods of adiabatic calorimetry and optic-mechanical dilatometry in the temperature range 100-370 K. Three blurred anomalies on the C-p(T) and alpha(T) dependencies are observed in the temperature range 200-360 K. The results of the studies are discussed together with data on the structure and dielectric properties in the framework of spherical random bond-random field model.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Li, Mingze, Li, Yawen, Molokeev M. S., Zhao, Jing, Na, Guangren, Zhang, Lijun, Xia, Zhiguo
Заглавие : Halogen substitution in zero-dimensional mixed metal halides toward photoluminescence modulation and enhanced quantum yield
Место публикации : Adv. Opt. Mater. - 2020. - Vol. 8, Is. 16. - Ст.2000418. - ISSN 2195-1071, DOI 10.1002/adom.202000418
Примечания : Cited References: 34. - M.L., Y.L. contributed equaly to this work. This work was supported by the National Natural Science Foundation of China (51961145101, 51972118, and 51722202), Fundamental Research Funds for the Central Universities (FRFTP-18-002C1), the Guangdong Provincial Science &Technology Project (2018A050506004), and the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (2017BT01 x 137). This work was also funded by RFBR according to the research project No. 19-52-80003. The work at Jilin University is supported by the National Natural Science Foundation of China (Grant No. 61722403 and 11674121) and Jilin Province Science and Technology Development Program (Grant No. 20190201016JC). Calculations were performed in part at the high performance computing center of Jilin University.
Предметные рубрики: WHITE-LIGHT EMISSION
PEROVSKITES
EXCITONS
Аннотация: Zero‐dimensional (0D) organic−inorganic hybrid metal halides haveunprecedented degrees of freedom for structural tunability and photoluminescence modulation. Here, the 0D isomorphic hybrid metal mixed halides (C9NH20)9Pb3Zn2Br19(1−x )Cl19x (x = 0–1) with continuous halogen contents control, exhibiting tunable emission and enhancement of photoluminescence quantum yield (PLQY) are reported. The competitive bromine to chlorine substitution process in (C9NH20)9Pb3Zn2Br19(1−x )Cl19x occurs first in [ZnBr4−x Clx ]2− tetrahedron before the [Pb3Br11−x Clx ]5− trimer. The increasing Cl content in samples from x = 0 to 1 results in an expected blue shift of emission peak from 565 to 516 nm, and meanwhile a strikingly room temperature PL quantum yield increase from 8% to 91%. Combined experimental characterizations and theoretical calculations indicate that the blue shift of interband transition energy is responsible for the emission peak shift. Moreover, with the increasing Cl content, the enhanced electron−phonon interaction and the weakened thermal‐assisted nonradiative recombination result in more efficient radiative transition channels and ultimately enhanced PLQY. The impact of halogen substitution on electronic structures and optical properties in 0D hybrid metal halides is emphasized in this work as a new strategy to promote the future development of new luminescent materials.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Deng, Chenkai, Hao, Shiqiang, Liu, Kunjie, Molokeev M. S., Wolverton, Christopher, Fan, Liubing, Zhou, Guojun, Chen, D.a., Zhao, Jing, Liu, Quanlin
Заглавие : Broadband light emitting zero-dimensional antimony and bismuth-based hybrid halides with diverse structures
Коллективы : Beijing Municipal Natural Science FoundationBeijing Natural Science Foundation [2182080]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [51972021, 51702329]; Fundamental Research Funds for the Central UniversitiesFundamental Research Funds for the Central Universities [FRF-IDRY-19-005]; RFBRRussian Foundation for Basic Research (RFBR) [19-52-80003]; Department of Energy, Office of Science Basic Energy SciencesUnited States Department of Energy (DOE) [DE-SC0014520]
Место публикации : J. Mater. Chem. C. - 2021. - Vol. 9, Is. 44. - P.15942-15948. - ISSN 2050-7526, DOI 10.1039/d1tc04198c. - ISSN 2050-7534(eISSN)
Примечания : Cited References: 52. - This work was supported by Beijing Municipal Natural Science Foundation (2182080) and the National Natural Science Foundation of China (51972021 and 51702329). The work was partly supported by the Fundamental Research Funds for the Central Universities (FRF-IDRY-19-005) and by the RFBR according to the research project No. 19-52-80003. S. H. and C. W. (DFT calculations) acknowledge support from the Department of Energy, Office of Science Basic Energy Sciences under Grant DE-SC0014520. Access to QUEST, the supercomputing resources facilities at Northwestern University, is also acknowledged
Предметные рубрики: CRYSTAL-STRUCTURE
LONE-PAIR
EMISSION
PEROVSKITES
TIN
LUMINESCENCE
Аннотация: Low-dimensional organic–inorganic metal halides have recently attracted extensive attention because of their various structures and distinguished photoelectric properties. Herein, we report a series of new zero-dimensional organic–inorganic hybrid metal halides: (TMEDA)3Bi2Cl12·H2O, (TMEDA)3Bi2Br12·H2O, (TMEDA)3Sb2Br12·H2O, and (TMEDA)5Sb6Cl28·2H2O [TMEDA = N,N,N′·trimethylethylenediamine]. (TMEDA)3M2X12·H2O (M = Bi or Sb, X = Cl or Br) crystallizes in the monoclinic space group P21/n, and (TMEDA)5Sb6Cl28·2H2O crystallizes in the orthorhombic space group Pnma. (TMEDA)3M2X12 possesses a zero-dimensional structure with the metal halide ions of [MBr6]3− isolated by the organic TMEDA2+ cations. Interestingly, the (TMEDA)5Sb6Cl28·2H2O structure consists of a combination of corner-connected octahedra [Sb4Cl18]6− and edge-shared [Sb2Cl10]4−, which is quite rare. The light emission of all these compounds was measured, and (TMEDA)3Sb2Br12·H2O exhibits the most intense luminescence. Upon 400 nm ultraviolet light excitation, (TMEDA)3Sb2Br12·H2O exhibited strong broadband yellow emission centered at 625 nm with a full-width at half-maximum of ∼150 nm originating from self-trapped excitons. This work suggests the possibility of new types of hybrid halides by introducing different metal centers and probing the structural evolution and photoluminescent properties, serving as a reference for the relationship between structure and luminescent performance and demonstrating their potential use as phosphors in light-emitting diodes.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhou, Jun, Li, Mingze, Molokeev M. S., Sun, Jiayue, Xu, Denghui, Xia, Zhiguo
Заглавие : Tunable photoluminescence in Sb3+-doped zero-dimensional hybrid metal halides with intrinsic and extrinsic self-trapped excitons
Место публикации : J. Mater. Chem. C. - 2020. - Vol. 8, Is. 15. - P.5058-5063. - ISSN 2050-7526, DOI 10.1039/d0tc00391c. - ISSN 2050-7534(eISSN)
Примечания : Cited References: 33. - This work is supported by the National Natural Science Foundation of China (No. 51722202, 51961145101, 51972118, 21576002 and 61705003), Fundamental Research Funds for the Central Universities (D2190980), the Guangdong Provincial Science & Technology Project (2018A050506004), and Beijing Technology and Business University Research Team Construction Project (No. PXM2019_014213_000007). This work was also funded by RFBR according to the Research Project No. 19-52-80003.
Предметные рубрики: WHITE-LIGHT EMISSION
LUMINESCENCE
PEROVSKITES
CS2NASCCL6
CS2NAYCL6
Аннотация: Dopants in luminescent metal halides provide an alternative way for photoluminescence tuning towards versatile optical applications. Here we report a trivalent antimony (Sb3+)-doped single crystalline 0D metal halide with the composition of (C9NH20)9[Pb3Cl11](ZnCl4)2:Sb3+. This compound possessed the coexistence of two emission centers including intrinsic and extrinsic self-trapped excitons (STEs), which are ascribed to [Pb3Cl11]5− clusters and triplet STEs formed by the 3P1–1S0 transition of Sb3+. By regulating the Sb3+ concentration, the emission can be tuned from green to yellow and finally to orange, which would help to develop optically pumped white light-emitting diodes (WLEDs) with different photometric characteristics. Moreover, this dopant-induced extrinsic STE approach presents a new direction towards tuning the luminescence properties of 0D metal halides, and may find application in environmentally-friendly, high-performance metal halide light emitters.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Li, Mingze, Zhou, Jun, Zhou, Guojun, Molokeev M. S., Zhao, Jing, Morad, Viktoriia, Kovalenko, Maksym, V, Xia, Zhiguo
Заглавие : Hybrid Metal Halides with Multiple Photoluminescence Centers
Место публикации : Angew. Chem. Int. Edit. - 2019. - Vol. 58, Is. 51. - P.18670-18675. - ISSN 1433-7851, DOI 10.1002/anie.201911419. - ISSN 1521-3773(eISSN)
Примечания : Cited References: 42. - This work is supported by the National Natural Science Foundation of China (Nos. 51722202 and 51972118), Fundamental Research Funds for the Central Universities (D2190980), the Guangdong Provincial Science & Technology Project (2018A050506004) and by European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. [819740], project SCALE-HALO).
Предметные рубрики: LIGHT EMISSION
PEROVSKITES
BR
Аннотация: Very little is known about the realm of solid‐state metal halide compounds comprising two or more halometalate anions. Such compounds would be of great interest if their optical and electronic properties could be rationally designed. Herein, we report a new example of metal halide cluster‐assembled compound (C9NH20)9[Pb3Br11](MnBr4)2, featuring distinctly different anionic polyhedra, namely, a rare lead halide cluster [Pb3Br11]5− and [MnBr4]2−. In accordance with its multinary zero‐dimensional (0D) structure, this compound is found to contain two distinct emission centers, 565 nm and 528 nm, resulting from the formation of self‐trapped excitons and 4T1‐6A1 transition of Mn2+ ions, respectively. Based on the high durability of (C9NH20)9[Pb3Br11](MnBr4)2 upon light and heat, as well as high photoluminescence quantum yield (PLQY) of 49.8 % under 450 nm blue light excitation, white light‐emitting diodes (WLEDs) are fabricated, showcasing its potential in backlight application.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Li, Mingze, Molokeev M. S., Zhao, Jing, Xia, Zhiguo
Заглавие : Optical functional units in zero-dimensional metal halides as a paradigm of tunable photoluminescence and multicomponent chromophores
Место публикации : Adv. Opt. Mater. - 2020. - Vol. 8, Is. 8. - Ст.1902114. - ISSN 2195-1071, DOI 10.1002/adom.201902114
Примечания : Cited References: 38. - This work was supported by the National Natural Science Foundation of China (Nos. 51961145101, 51722202, and 51972118), Fundamental Research Funds for the Central Universities (D2190980), the Guangdong Provincial Science & Technology Project (2018A050506004), and this work was also funded by RFBR according to the Research Project No. 19-52-80003
Предметные рубрики: PEROVSKITES
LUMINESCENCE
ABSORPTION
EMISSION
Аннотация: Zero-dimensional (0D) organic–inorganic hybrid luminescent metal halides have many promising optoelectronic applications; however, the single building unit in the 0D framework restricts their multimode optical control and photoluminescence tuning. Thus, it remains urgent but challenging to rationally design distinct anionic polyhedral with different optical functions and further expand this family by an equivalent cation substitution and halogen replacement. Herein, (C9NH20)9[Pb3X11](MX4)2 (X = Br and Cl, M = Mn, Fe, Co, Ni, Cu, and Zn) is successfully synthesized verifying the rationality of the design philosophy, and the optical characterizations demonstrate the effects of X‐position anions and M‐position cations on luminescence process. Intriguingly, both [Pb3X11]5− and [MX4]2− perform as inorganic building units in this 0D system and optically active centers, in which the former leads to high‐efficiency broad‐band yellow/green emission originating from self‐trapped excitons and the as‐observed multicomponent chromophores are derived from the absorption of the latter in the visible light region. The present work highlights the importance of different optical functional units showing synergistic effects on the physical properties and inspires future studies to explore multifunctional application of 0D luminescent metal halides.
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11.

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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12.

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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13.

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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14.

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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15.

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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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zinenko V. I., Pavlovskii M. S.
Заглавие : Lattice dynamics and the phase transition from the cubic phase to the tetragonal phase in the LaMnO3 crystal within the polarizable-ion model
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2007. - Vol. 49, Is. 9. - P1749-1758. - ISSN 1063-7834, DOI 10.1134/S1063783407090235
Примечания : Cited References: 23
Предметные рубрики: NEUTRON-DIFFRACTION
PEROVSKITES
MANGANITES
PHONONS
Аннотация: The paper reports on the results of ab initio calculations of the static and dynamic properties of the LaMnO3 crystal with a perovskite structure in the cubic, rhombohedral, and orthorhombic phases. The calculations are performed within the ionic crystal model, which takes into account the deformability and polarizability of the ions. It is revealed that the spectrum of lattice vibrations in the cubic phase contains unstable vibrational modes, which occupy the phase space in the entire Brillouin zone. The eigenvectors of the softest mode at the boundary point R of the Brillouin zone are associated with the displacements of the oxygen ions and correspond to the "rotation" of the MnO6 octahedron. The condensation of one, two, and three components of this mode leads to the tetragonal, orthorhombic, and rhombohedral distortions of the structure. The structural phase transition is described in terms of the local mode approximation with the use of the double perovskite unit cell, in which the MnO6 octahedron is explicitly separated. The parameters of the model Hamiltonian are determined. The static properties are investigated by the Monte Carlo method. The calculated temperature of the phase transition from the cubic phase (9800 K) is considerably higher than the melting temperature of the crystal under investigation. The calculated frequencies of long-wavelength lattice vibrations in the experimentally observed orthorhombic and rhombohedral phases are in reasonable agreement with experimental data.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aplesnin S. S.
Заглавие : Effect of bond fluctuations on the transport properties of manganites and nickelates
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2007. - Vol. 104, Is. 5. - P766-774. - ISSN 1063-7761, DOI 10.1134/S1063776107050111
Примечания : Cited References: 26
Предметные рубрики: NEUTRON-DIFFRACTION
CHARGE DISPROPORTIONATION
ELECTRONIC-STRUCTURE
MAGNETIC ORDER
TRANSITIONS
PEROVSKITES
PRNIO3
GAP
Ключевые слова (''Своб.индексиров.''): crystal structure--manganites--optimization--thermal conductivity--thermal effects--bond fluctuations--nickelates--orthorhombic crystal structure--nickel compounds
Аннотация: For the manganites RMnO(3) (R = La, Pr, Nd), a mechanism is proposed to explain the anomalous temperature dependences of the kinetic coefficients, resistivity, and thermoelectric power during the transition from the pseudocubic O to the orthorhombic O' crystal structure. The contributions of the bending and stretching modes of the octahedron to the formation of thermal-conductivity maxima and to the deviation from the linear dependence of ln(rho/T) on 1/T at low temperatures have been estimated. In nickelates, the metal-insulator transition is caused by lattice-polaron pinning by the stretching mode of the octahedron, and the low-temperature anomaly of the thermal conductivity is related to electron scattering by the bending mode of the octahedron.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Volkov N. V., Eremin E. V., Shaykhutdinov K. A., Tsikalov V. S., Petrov M. I., Balaev D. A., Semenov S. V.
Заглавие : The magnetic-field-driven effect of microwave detection in a manganite granular system
Место публикации : J. Phys. D. - 2008. - Vol. 41, Is. 1. - Ст.15004. - ISSN 0022-3727, DOI 10.1088/0022-3727/41/1/015004
Примечания : Cited References: 24
Предметные рубрики: IDENTICAL METALS
TUNNEL-JUNCTIONS
MAGNETORESISTANCE
RECTIFICATION
SPINTRONICS
TEMPERATURE
PEROVSKITES
Ключевые слова (''Своб.индексиров.''): bias currents--curie temperature--electric power generation--granular materials--magnetic field effects--microwave irradiation--voltage measurement--direct current voltage--magnetic tunnel junctions--metal insulator metal junctions--nonmagnetic metals--manganites
Аннотация: We demonstrate the microwave detection effect in a granular La0.7Ca0.3MnO3 sample. Dc voltage generated by the sample in response to microwave irradiation below the Curie temperature is found to be dependent on the applied magnetic field. The magnetic field dependence of the dc voltage has a broad peak resembling an absorption line. The detection effect depends substantially on the magnetic history of the sample; however, identical measurement conditions provide reproducibility of the experimental results. The detected dc voltage increases linearly with microwave power and strongly depends on a bias current through the sample. According to the results of systematic measurements, there exist two contributions to a value of the detected output signal. The first is magneto-independent; it can be explained in the framework of a mechanism used traditionally for description of the rectification effect in metal-insulator-metal junctions with nonmagnetic metals. The other is magneto-dependent; it originates from the interplay between the spin-dependent current through magnetic tunnel junctions and spin dynamics of the grains, which form these junctions in the sample.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zhandun V. S., Zamkova N. G., Zinenko V. I.
Заглавие : Lattice dynamics, ferroelectric and antiferroeelctric instabilities, and the ferroelectric phase transition in disordered PbB(1/2)' B(1/2)'' O(3) (B ' = Ga, In, Lu; B '' = Nb, Ta) solid solutions
Разночтения заглавия :авие SCOPUS: Lattice dynamics, ferroelectric and antiferroeelctric instabilities, and the ferroelectric phase transition in disordered PbB′ 1/2B″1/2O3 (B′ = Ga, In, Lu; B″ = Nb, Ta) solid solutions
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2008. - Vol. 106, Is. 6. - P1109-1117. - ISSN 1063-7761, DOI 10.1134/S1063776108060101
Примечания : Cited References: 29
Предметные рубрики: STATISTICAL-MECHANICS
PEROVSKITES
CRYSTALS
ORDER
RELAXOR
BATIO3
PBTIO3
Ключевые слова (''Своб.индексиров.''): crystal lattices--ferroelectricity--lattice vibrations--solids--ferroelectric (barium strontium titanate)--ferroelectric phase transitions--lattice (co)--lattice dynamics--vibration spectrum--ferroelectric materials
Аннотация: The lattice vibration spectra, rf permittivity, and dynamic Born charges of disordered PbB(1/2)'B(1/2)'' O(3) (B' = Ga, In, Lu; B '' = Nb, Ta) solid solutions are calculated in terms of the generalized Gordon-Kim model. All the compounds are found to have soft modes related to the center (Gamma(15)) and boundary point R (R(15)) of the Brillouin zone; the frequencies of these modes are close. The ferroelectric phase transition temperatures and the spontaneous polarization in the ferroelectric phase are calculated for the solid solutions using a model Hamiltonian in the local mode approximation and the Monte Carlo method. These temperatures for the tantalum compounds are found to be higher than for the niobium compounds, and temperature t(s) increases with the atomic number of ion B'. A model where the antiferroelectric state is related to the condensation of modes Gamma(15) and R(15) is proposed. It is found that, for all compounds except for PbSc(1/2)Nb(1/2)O(3) and PbSc(1/2)Ta(1/2)O(3), the ferroelectric phase, which is only related to the condensation of mode R(15), and the antiferroelectric phase have similar energies. In PbIn(1/2)Ta(1/2)O(3), the antiferroelectric phase turns out to be energetically favorable.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Zinenko V. I., Zamkova N. G.
Заглавие : Ab initio calculation of the ferroelectric phase transition in disordered and ordered PbSc0.5Ta0.5O3 and PbSc0.5Nd0.5O3 solid solutions with the use of a model Hamiltonian
Разночтения заглавия :авие SCOPUS: Ab initio calculation of the ferroelectric phase transition in disordered and ordered PbSc0.5Ta0.5O3 and PbSc 0.5Nd0.5O3 solid solutions with the use of a model Hamiltonian
Место публикации : J. Exp. Theor. Phys.: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2008. - Vol. 106, Is. 3. - P542-549. - ISSN 1063-7761, DOI 10.1134/S1063776108030138
Примечания : Cited References: 17
Предметные рубрики: RELAXOR FERROELECTRICS
PEROVSKITES
BATIO3
PBTIO3
Ключевые слова (''Своб.индексиров.''): approximation theory--ferroelectric materials--hamiltonians--mathematical models--monte carlo methods--phase transitions--ferroelectric phase transition--gordon-kim model--local-mode approximation--solid solutions
Аннотация: To describe the ferroelectric phase transition in ordered and disordered PbSc0.5Ta0.5O3 (PST) and PbSc0.5Nd0.5O3 (PSN) solid solutions, a model Hamiltonian is written in the local-mode approximation, in which long-range dipole-dipole and short-range interactions of local modes are taken into account. The Hamiltonian parameters are determined from the set of energies of a series of distorted structures, calculated within the nonempirical generalized Gordon-Kim model. The statistical mechanics of the systems with a model Hamiltonian is investigated by the Monte Carlo method. It is revealed that PSN solid solutions undergo a transition to the ferroelectric rhombohedral phase through an intermediate phase, existing in a narrow temperature range. PST solid solutions undergo a ferroelectric phase transition directly from the paraelectric cubic to the ferroelectric rhombohedral phase.
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