Библиотека института физики им. Л.В. Киренского СО РАН

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Каталог книг и брошюр библиотеки ИФ СО РАН

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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pogoreltsev E. I., Bogdanov E. V., Melnikova S.V., Flerov I. N., Laptash N. M.
Заглавие : (NH4)3HfF7: Crystallooptical and calorimetric studies of a number of successive phase transitions
Место публикации : J. Fluor. Chem.: Elsevier, 2017. - Vol. 204. - P.45-49. - ISSN 00221139 (ISSN), DOI 10.1016/j.jfluchem.2017.10.004
Примечания : Cited References: 14
Аннотация: Single crystals of (NH4)3HfF7 were grown. Polarising optical observations as well as measurement of the heat capacity and birefringence Δn(Т) were performed in the temperature range of 200–310 K. Reversible phase transitions at temperatures T0 = 290 K, Т1 = 280.5 K, Т2 ≈ 273 K, Т3 = 266 K, Т4 = 259 K, Т5 = 231 K, Т6 = 229 K were found. Observations in polarised light make it possible to suggest a sequence of changes in the symmetry groups for these transitions: Fm3m ⟵Т0→ cub. ⟵Т1→ mmm (1) ⟵Т2→ mmm (2) ⟵Т3→ mmm (3) ⟵Т5→ 2/c. The T-p phase diagram was studied and the temperature boundaries of the stability of the distorted crystalline phases were determined. A significant change of the entropy at successive phase transitions ΣΔS = 10.6 J/mol K indicates a disordering of the initial cubic phase.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Chen Y., Liu F., Zhang Z., Hong J., Molokeev M. S., Bobrikov I. A., Shi J., Zhou J., Wu M.
Заглавие : A novel Mn4+-activated fluoride red phosphor Cs30(Nb2O2F9)9(OH)3·H2O:Mn4+ with good waterproof stability for WLEDs
Место публикации : J. Mater. Chem. C. - 2022. - Vol. 10, Is. 18. - P.7049-7057. - ISSN 20507534 (ISSN), DOI 10.1039/d2tc00132b
Примечания : Cited References: 56. - This work was financially supported by grants from the National Natural Science Foundation of China (NSFC) (No. 51802359), the Joint Funds of NSFC and Yunnan Province (No. U1702254), and Guangdong Basic and Applied Basic Research Foundation (No. 2020A1515010556)
Аннотация: Red-light-emitting materials, as pivotal components of warm white light-emitting diodes (WLEDs), have drawn increasing public focus. Among these, Mn4+-doped red light-emitting fluorides have drawn considerable attention when combined with an InGaN chip; however, they suffer from poor water stability under humid conditions. In this work, a novel fluoride red phosphor, Cs30(Nb2O2F9)9(OH)3·H2O:xMn4+ (CNOFM), with good water resistance was synthesized for the first time using a facile co-precipitation method at ambient temperature. Experiments were implemented for the precise analysis of its crystal structure, optical properties, micro-morphology, thermal behavior, and waterproof properties. 6.66% Mn4+-doped CNOFM maintained a stable crystal structure and possessed strong PL intensity located at 633 nm with high color purity of 96%. CNOFM showed better thermal and waterproof stability compared with the commercial K2SiF6:Mn4+ red phosphor. Without any surface modifications, the PL intensity remained at about 83% of the initial value after immersion in water for 60 min, and the mechanism was investigated. Finally, a warm WLED with a CRI of 92.3 and CCT of 3271 K was fabricated using the CNOFM red phosphor.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M. V., Kartashev A. V., Bogdanov E. V., Flerov I. N., Laptash N. M.
Заглавие : Calorimetric, dilatometric and DTA under pressure studies of the phase transitions in elpasolite (NH4)2KZrF7
Место публикации : J. Fluor. Chem. - 2020. - Vol. 235. - Ст.109523. - ISSN 00221139 (ISSN), DOI 10.1016/j.jfluchem.2020.109523
Примечания : Cited References: 45. - The reported study was funded by RFBR according to the research project No. 18-02-00269 a. X-ray and dilatometric data were obtained using the equipment of Krasnoyarsk Regional Center of Research Equipment of Federal Research Center "Krasnoyarsk Science Center SB RAS"
Аннотация: Heat capacity, thermal expansion, and sensitivity to the hydrostatic pressure of (NH4)2KZrF7 elpasolite are studied in a wide temperature range. The changes in deformation and entropy during successive phase transitions are determined: Δ(ΔV/V) = 3·10−4; ΔS = 8 J/mol K The temperatures and entropies of phase transitions turned out to be slightly sensitive to pressure changes. An analysis of the entropy of phase transformations was performed in the framework of the model of the cubic phase structure Fm-3 m. In the low temperature phase, an anomalous behavior of thermodynamic properties, which is not characteristic of phase transitions, was observed, accompanied by a significant change in the crystal lattice entropy.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Fokina V. D., Bovina A. F., Bogdanov E. V., Pogoreltsev E. I., Laptash N. M.
Заглавие : Disorder and phase transitions in oxyfluoride (NH4)(3)Ta(O-2)(2)F-4
Место публикации : J. Fluor. Chem. - 2011. - Vol. 132, Is. 10. - P.713-718. - ISSN 0022-1139, DOI 10.1016/j.jfluchem.2011.05.012
Примечания : Cited Reference Count: 19. - Гранты: This work was supported by the Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools of the Russian Federation (NSh-4645.2010.2).Финансирующая организация: Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools of the Russian Federation [NSh-4645.2010.2]
Предметные рубрики: HEAT-CAPACITY
COMPLEXES
RB2KTIOF5
FLUORIDES
CRYOLITE
Ключевые слова (''Своб.индексиров.''): cubic oxyfluorides--structural disorder--phase transitions--entropy--permittivity--pressure effect--cubic oxyfluorides--entropy--permittivity--phase transitions--pressure effect--structural disorder
Аннотация: Calorimetric, X-ray, dielectric and DTA under pressure measurements have been performed on oxyfluoride (NH4)(3)Ta(O-2)(2)F-4. The succession of nonferroelectric phase transitions was found associated with the order-disorder processes. The comparative analysis tantalate with related niobate has revealed the important role of the central atom in the physical properties behavior, mechanism of structural distortions and barocaloric effect in oxyfluorides with the eight-coordinated anionic polyhedra. (C) 2011 Elsevier By. All rights reserved.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bogdanov E. V., Vasil'ev A. D., Flerov I. N., Laptash N. M.
Заглавие : Effect of cation substitution in fluorine-oxygen molybdates (NH4)(2-x) A (x) MoO2F4
Разночтения заглавия :авие SCOPUS: Effect of cation substitution in fluorine-oxygen molybdates (NH4)2 - xAxMoO2F4
Место публикации : Phys. Solid State: MAIK NAUKA/INTERPERIODICA/SPRINGER, 2011. - Vol. 53, Is. 2. - P303-308. - ISSN 1063-7834, DOI 10.1134/S1063783411020065
Примечания : Cited References: 11. - This study was supported by the Russian Foundation for Basic Research (project no. 09-02-00062) and the Council on Grants from the President of the Russian Federation for Support of Leading Scientific Schools of the Russian Federation (project no. NSh-1011.2008.2).
Предметные рубрики: PHASE-TRANSITIONS
CRYSTALS
(NH4)(2)WO2F4
DIFFRACTION
OXYFLUORIDE
MECHANISM
DISORDER
Аннотация: Thermophysical and structural studies of (NH4)(2 - x) A (x) MoO2F4 (A = Cs, Rb, K) solid solutions of oxyfluorides have been performed. The character of the influence of cation substitutions on the stability of the initial phase (space group Cmcm) and on the mechanism of phase transitions has been elucidated.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Wu, Po-Chang, Chen, Hsin-Li, Rudakova, Natalya V., Timofeev I. V., Zyryanov V. Ya., Lee, Wei
Заглавие : Electro-optical and dielectric properties of polymer-stabilized blue phase liquid crystal impregnated with a fluorine-containing compound
Коллективы : Ministry of Science and Technology, Taiwan [104-2112-M-009-008-MY3, 106-2923-M-009-002-MY3]; Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund [16-42-240704, 17-42-240464]
Место публикации : J. Mol. Liq. - 2018. - Vol. 267. - P.138-143. - ISSN 0167-7322, DOI 10.1016/j.molliq.2017.12.062. - ISSN 1873-3166(eISSN)
Примечания : Cited References: 47. - The authors are indebted to Prof. Mon-Juan Lee of Chang-Jung Christian University for valuable discussions on photopolymerization. This work was financially supported by the Ministry of Science and Technology, Taiwan, through Grant Nos. 104-2112-M-009-008-MY3 and 106-2923-M-009-002-MY3, and by the Russian Foundation for Basic Research, Government of Krasnoyarsk Territory, Krasnoyarsk Region Science and Technology Support Fund to the research projects 16-42-240704 and 17-42-240464.
Предметные рубрики: HYSTERESIS
TEMPERATURE
MONOMERS
Ключевые слова (''Своб.индексиров.''): polymer-stabilized blue phase--liquid crystal--fluorine-containing--compound--operating voltage--ionic effect
Аннотация: The effects of a fluorine-containing compound (4,4′-difluorobenzophenone; DF) on the electro-optical and dielectric properties of polymer-stabilized blue phase (PSBP) liquid crystals were investigated. When a PSBP cell was driven by an in-plane electric field, the addition of DF up to 2.7 wt% effectively reduced the operation voltage by ~ 30%. Further inspection by dielectric spectroscopy indicated that the ionic concentration in PSBP decreased with increasing loading of DF. This finding can be ascribed to the complexation of impurity ions near the ketone group and carbon–fluorine bonds of the DF compound that restrained the ion transport after photopolymerization. As a result, the DF compound can be regarded as a superior ion-suppressor, enabling the reduction in the ionic effect and, in turn, the promotion of the electro-optical response of a PSBP.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Pogoreltsev E. I., Flerov I. N., Kartashev A. V., Bogdanov E. V., Laptash N. M.
Заглавие : Heat capacity, entropy, dielectric properties and T–p phase diagram of (NH4)3TiF7
Коллективы : Russian Foundation for Basic Research [15-02-02009]; Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools of the Russian Federation [NSh-924.2014.2]
Место публикации : J. Fluor. Chem.: Elsevier Science, 2014. - Vol. 168. - P.247-250. - ISSN 0022-1139, DOI 10.1016/j.jfluchem.2014.10.016. - ISSN 1873-3328
Примечания : Cited References: 16. - This work was supported by the Russian Foundation for Basic Research (Grant no. 15-02-02009), and the Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools of the Russian Federation (Grant no. NSh-924.2014.2).
Предметные рубрики: CRYSTAL-STRUCTURE
TRANSITIONS
FLUORIDES
NH4F
Ключевые слова (''Своб.индексиров.''): cubic fluorides--phase transitions--dielectric--phase diagram--calorimetry
Аннотация: Successive phase transitions G1 -- G2 -- G3 in the double salt (NH4)(3)TiF7 have been studied by detailed calorimetric, DTA under hydrostatic pressure and dielectric measurements. Rather large entropy jumps at phase transition points were found to be followed by large additional contributions associated with the temperature dependence of the excess heat capacity. The permittivity behaviour and the tangent of the dielectric losses proved the nonferroelectric nature of both transformations. Two triple-points were found on the temperature-pressure phase diagram, suggesting the existence of a hypothetical parent G0 = Pm-3m cubic phase. A direct transformation between high (G0) and low (G3) temperature cubic phases takes place at p 0.41 GPa with a baric coefficient dT(G0) -- (G3)/dp = -40 K/GPa. (C) 2014 Elsevier B.V. All rights reserved.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Kartashev A. V., Pogorel'tsev E. I., Laptash N. M.
Заглавие : Heat capacity, thermal expansion and barocaloric effect in fluoride K2TaF7
Место публикации : J. Mater. Sci. - 2019. - Vol. 54, Is. 23. - P.14287–14295. - ISSN 00222461 (ISSN), DOI 10.1007/s10853-019-03924-8
Примечания : Cited References: 20. - The reported study was funded by RFBR according to the research Project No. 18-02-00269_a.
Аннотация: The heat capacity and thermal expansion of potassium heptafluorotantalate were studied. The room temperature phase P21/c is stable at least to 4 K. The strong first-order phase transition P21/c−Pnma at T0=486.2K is accompanied by giant changes in the entropy, ΔS0=22.3J(molK)−1, and volume strain, δV0/V=−3.6%. A rather high sensitivity of K2TaF7 to pressure was found, dT0/dp=−220KGPa−1. Significant extensive and intensive barocaloric effects are found at low pressure. The possibility of improving the barocaloric properties is discussed.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Dubrovskiy A. A., Knyazev Yu. V., Gerasimova Yu. V., Udovenko A. A., Laptash N. M.
Заглавие : Influence of the Jahn-Teller effect on magnetic anisotropy in single crystals of fluorine hexahydrates of transition metals
Место публикации : Phys. Solid State. - 2022. - Vol. 64, Is. 11. - P.1709-1712. - ISSN 10637834 (ISSN), DOI 10.21883/PSS.2022.11.54194.406. - ISSN 10906460 (eISSN)
Примечания : Cited References: 16. - The work was done with financial support from the Russian Foundation for Basic Research, Government of Krasnoyarsk Krai and the Krasnoyarsk Krai Foundation of Science within the research project No. 20-42-240014
Аннотация: The magnetic properties of fluorine hexahydrates of transition metals have been studied. It was found that the presence of spin-orbit interaction of the transition metal ion has a significant effect on anisotropy of magnetic properties. Depending on the direction of interaction of the orbital magnetic moment of a transition metal cation with a crystal field easy direction of magnetization changes from the crystallographic b-axis to the c-axis.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Avramov P. V., Fedorov D. G., Sorokin P. B., Sakai S., Entani S., Ohtomo M., Matsumoto Y., Naramoto H.
Заглавие : Intrinsic edge asymmetry in narrow zigzag hexagonal heteroatomic nanoribbons causes their subtle uniform curvature
Место публикации : J. Phys. Chem. Lett. - 2012. - Vol. 3, Is. 15. - P.2003-2008. - ISSN 1948-7185, DOI 10.1021/jz300625t
Примечания : Cited References: 42. - This work was supported by JAEA Research fellowship (P.V.A.). P.V.A. also acknowledges JAEA ASRC and the Molecular Spintronics Group for hospitality and fruitful collaboration. D.G.F. thanks Prof. Kazuo Kitaura for many fruitful discussions and the Next Generation SuperComputing Project, Nanoscience Program and Strategic Programs for Innovative Research (MEXT, Japan) for financial support. This work was partially supported by Russian Ministry of Education and Science (Contract No. 16.552.11.7014) (P.B.S.).
Предметные рубрики: MOLECULAR-ORBITAL METHOD
WALLED CARBON NANOTUBES
GRAPHENE NANORIBBONS
ELECTRONIC-STRUCTURE
OPTICAL-TRANSITIONS
SOLIDS
BOND
Aromatic rings
Conical surfaces
Finite length
Fragment molecular orbital methods
Graphene nanoribbons
Intrinsic curvature
Nanoribbons
Out-of-plane
Structural stress
Ключевые слова (''Своб.индексиров.''): zigzag nanoribbons--hexagonal atomic lattices--fluorine-terminated graphene
Аннотация: The atomic and electronic structure of narrow zigzag nanoribbons with finite length, consisting of graphene terminated by fluorine on one side, hexagonal (h) h-BN, and h-SiC were studied with density functional theory. It is found that the asymmetry of nanoribbon edges causes a uniform curvature of the ribbons due to structural stress in the aromatic ring plane. Narrow graphene nanoribbons terminated with fluorine on one side demonstrate a considerable out-of-plane bend, suggesting that the nanoribbon is a fraction of a conical surface. It is shown that the intrinsic curvature of the narrow nanoribbons destroys the periodicity and results in a systematic cancellation of the dipole moment. The in- and out- of-plane curvature of thin arcs allows their closure in nanorings or cone fragments of giant diameter. Using the fragment molecular orbital method, we optimized the structure of a planar giant arc and a closed ring of h-BN with a diameter of 105 nm.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M. V., Molokeev M. S., Kartashev A. V., Pogoreltsev E. I., Mel'nikova S. V., Laptash N. M., Flerov I. N.
Заглавие : Investigation of thermal properties and structure of complex fluoride K3ZrF7
Место публикации : J. Fluor. Chem. - 2021. - Vol. 241. - Ст.109677. - ISSN 00221139 (ISSN), DOI 10.1016/j.jfluchem.2020.109677
Примечания : Cited References: 44. - The reported study was funded by RFBR according to the research project No. 18-02-00269 a. X-ray and dilatometric data were obtained using the equipment of Krasnoyarsk Regional Center of Research Equipment of Federal Research Center "Krasnoyarsk Science Center SB RAS"
Аннотация: X-ray, calorimetric and dilatometric studies of K3ZrF7 revealed the existence of the phase transition Fm-3m ↔ R-3m at T0 = 320 K. The structural model assumes a disorder of a pentagonal bipyramid ZrF7 with the following ratio of equivalent orientation positions in the initial and distorted phases: 12 to 6. A good agreement was found between the experimental and model-calculated changes in strain and entropy during the phase transition. A comparative analysis of entropy and structural parameters of related fluorides K3ZrF7 - (NH4)2KZrF7 - (NH4)3ZrF7 was performed. The anomalous behavior of thermodynamic properties in the range 140−230 K is not typical for phase transitions and is accompanied by a significant change in the entropy of the crystal lattice.
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12.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Atuchin V. V., Gavrilova T. A., Kesler V. G., Molokeev M. S., Aleksandrov K. S.
Заглавие : Low-temperature synthesis and structural properties of ferroelectric K 3WO3F3 elpasolite
Место публикации : Chem. Phys. Lett. - 2010. - Vol. 493, Is. 1-3. - P.83-86. - ISSN 0009-2614, DOI 10.1016/j.cplett.2010.05.023
Примечания : Cited References: 37
Предметные рубрики: PEROVSKITE-LIKE OXYFLUORIDES
CORE-LEVEL SPECTROSCOPY
PHASE-TRANSITIONS
SOLID-STATE
ELECTRON-DIFFRACTION
DIFFUSE-SCATTERING
RHEED ANALYSIS
POLAR
BEHAVIOR
(NH4)(3)TIOF5
Ключевые слова (''Своб.индексиров.''): chemical synthesis--elpasolite--ferroelectric phase transition--fluorine atoms--low temperature synthesis--low temperatures--oxyfluorides--partial ordering--room temperature--sem--space groups--structure parameter--xrd--chemical properties--ferroelectric materials--ferroelectricity--fluorine--oxygen--phase transitions--rietveld method--single crystals--synthesis (chemical)--x ray photoelectron spectroscopy--x ray powder diffraction--scanning electron microscopy
Аннотация: Low-temperature ferroelectric G2 polymorph of K3WO 3F3 has been prepared by chemical synthesis. Structural and chemical properties of the final product have been evaluated with X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Structure parameters of G2-K 3WO3F3 are refined by the Rietveld method from XRD data measured at room temperature (space group Cm, Z = 2, a = 8.7350(3), b = 8.6808(5), c = 6.1581(3), ? = 135.124(3), V = 329.46(3) 3; RB = 2.47%). Partial ordering of oxygen and fluorine atoms has been found over anion positions. Mechanism of ferroelectric phase transition in A2BMO3F3 oxyfluorides is discussed. В© 2010 Elsevier B.V. All rights reserved.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Izosimova M. G., Livshits A. I., Buznik V. M., Fedorov P. P., Kkrivandina E. A., Sobolev B. P.
Заглавие : Mechanism of fluorine ion diffusion in tysonite-type solid electrolytes
Место публикации : Fiz. Tverd. Tela. - 1986. - Vol. 28, Is. 9. - P.2644-2647. - ISSN 0367-3294
Примечания : Cited References: 20
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mel'nikova S. V., Bogdanov E. V., Molokeev M. S., Laptash N. M., Flerov I. N.
Заглавие : Optical and calorimetric studies of K2TaF7
Место публикации : J. Fluor. Chem. - 2019. - Vol. 222-223. - P.75-80. - ISSN 00221139 (ISSN) , DOI 10.1016/j.jfluchem.2019.04.016
Примечания : Cited References: 26. - The reported study was funded by RFBR according to the research project № 18-02-00269.
Аннотация: Optical and calorimetric experiments on K2TaF7 are performed in a wide temperature range. No features were found in the behavior of the birefringence Δnb(T), the angle of rotation of the indicatrix ϕ(T) and the heat capacity ΔCp(T) except for those associated with the Pnma↔P21/c phase transition. Structural transformation was characterized as strong first order “proper” ferroelastic accompanied by a huge angle ϕ ≈40° and strong pre-transition phenomena in Δnb(T). Two contributions to the anomalies of the optical properties were found associated with the photoelastic effect and the transition parameter related linearly to the spontaneous deformation. Thermal treatments cause correlated changes in temperature and enthalpy of the phase transition, which leads to the invariance of the large magnitude of the corresponding entropy ΔS = 22 J/mol·K which does not match the model with the absence of structural disorder in the Pnma phase.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mel'nikova S. V., Laptash N. M., Pogoreltsev E. I.
Заглавие : Phase transformation in some hexahydrated metal(II) fluorogermanates and fluorotitanates: Optical and differential scanning calorimetry studies
Место публикации : J. Fluor. Chem. - 2022. - Vol. 263. - Ст.110048. - ISSN 00221139 (ISSN), DOI 10.1016/j.jfluchem.2022.110048
Примечания : Cited References: 31
Аннотация: Large single crystals of hydrated fluorides CoGeF6∙6H2O, FeGeF6∙6H2O, CoTiF6∙6H2O, and ZnTiF6∙6H2O were obtained and their birefringence and heat capacities have been studied. The compounds undergo a phase transition (PT) of the first order, which is accompanied by a change in optical anisotropy, twinning, and a decrease in the compound symmetry from trigonal (m, ) to monoclinic (Р21/c) in accordance with the rotation of the optical indicatrix around only one direction. The value of the entropy change during the PT is small for the first two compounds (0.36R and 0.34R) and large for the last two (0.76R and 0.95R).
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bogdanov E. V., Molokeev M. S., Gorev M. V., Kartashev A. V., Laptash N. M., Flerov I. N.
Заглавие : Phase transition in RbCdZrF7: Structure and thermal properties
Место публикации : J. Fluor. Chem. - 2021. - Vol. 245. - Ст.109748. - ISSN 00221139 (ISSN), DOI 10.1016/j.jfluchem.2021.109748
Примечания : Cited References: 30. - The reported study was funded by RFBR according to the research project No. 18-02-00269 a. X-ray and dilatometric data were obtained using the equipment of Krasnoyarsk Regional Center of Research Equipment of Federal Research Center "Krasnoyarsk Science Center SB RAS"
Аннотация: X-ray, calorimetric and dilatometric studies of RbCdZrF7 revealed the existence of the second order phase transition Cmcm - P21/m at T0 = 200 K. The structure of the initial and distorted phases is ordered. The phase transition is associated with displacements of fluorine atoms, which leads to minor rotations of the CdF7 and ZrF7 pentagonal bipyramids. A small change in entropy, 0.1R, is characteristic of displacive-type transformations. An anomalously high susceptibility of the transition temperature to hydrostatic pressure was found.
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17.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Molokeev M. S., Bogdanov E. V., Misyul S. V., Tressaud A., Flerov I. N.
Заглавие : Phase transitions in defect pyrochlore structure of CsFe2F6
Коллективы : European Symposium on Fluorine Chemistry (17; 2013 ; June ; 21-25; Paris, France)
Место публикации : 17th European Symposium on Fluorine Chemistry: Abstracts book. - 2013. - P.276
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M. V., Flerov I. N., Tressaud A., Molokeev M. S., Kartashev A. V., Pogoreltsev E. I., Bayukov O. A.
Заглавие : Phase transitions in fluoride KFe2F6 with tetragonal tungsten bronze structure
Коллективы : RFBR [12-02-00056]; Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools of the Russian Federation [NSh-924.2014.2]
Место публикации : J. Fluor. Chem.: Elsevier Science, 2014. - Vol. 168. - P.204-211. - ISSN 0022-1139, DOI 10.1016/j.jfluchem.2014.09.031. - ISSN 1873-3328
Примечания : Cited References: 14. - This work was supported by RFBR, project no. 12-02-00056, and the Council on Grants from the President of the Russian Federation for the Support of Leading Scientific Schools of the Russian Federation (grant NSh-924.2014.2).
Предметные рубрики: K3FE5F15
490-K
ORDER
Ключевые слова (''Своб.индексиров.''): tetragonal tungsten bronze structure--phase transition--charge ordering--thermal properties
Аннотация: Heat capacity, thermal dilatation, structure, Mossbauer spectra and dielectric permittivity of fluoride KFe2F6 with tetragonal tungsten bronze crystal structure were studied. The as-made sample undergoes two structural phase transitions P4/mbm (T-1 approximate to 340 K) - Pbam (T-2 approximate to 250 K) - G(2) and magnetic phase transformation at T-m approximate to 133 K. Heating up to 600-700 K and subsequent cooling in helium atmosphere leads to a change of phase transition temperatures and diffused anomalies in thermal expansion. The results obtained and influence of thermal prehistory of the sample on its physical properties are discussed in the context of previous studies on related fluorides KFe2F6, which sometimes suggest conflicting structural details. (C) 2014 Elsevier B.V. All rights reserved.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Flerov I. N., Molokeev M. S., Laptash N. M., Udovenko A. A., Pogoreltsev E. I., Mel'nikova S. V., Misyul S. V.
Заглавие : Structural transformation between two cubic phases of (NH4)3SnF7
Место публикации : J. Fluor. Chem.: Elsevier, 2015. - Vol. 178. - P.86-92. - ISSN 0022-1139, DOI 10.1016/j.jfluchem.2015.06.024
Примечания : Cited References: 19. - We thank T.A. Kaidalova for the idea of doubling the unit cell parameter of (NH4)3SnF7 at room temperature. The reported study was partially supported by RFBR, research project No. 15-02-02009 a.
Предметные рубрики: CRYSTAL-STRUCTURE
TRANSITION
NH4F
Ключевые слова (''Своб.индексиров.''): cubic fluorides--phase transitions--x-ray--calorimetry--crystal optics
Аннотация: Reinvestigations of the room temperature structure of ammonium heptafluorostannate (NH4)3SnF7 = (NH4)2SnF6·NH4F = (NH4)3[SnF6]F by both powder and single crystal X-ray diffractions have revealed that its real symmetry is Pa−3 (Z = 8) instead of Pm−3m (Z = 1) suggested earlier. Polarizing optical observations, heat capacity, X-ray powder, and single crystal measurements were performed in a wide temperature range (100–420 K). A reversible structural phase transition of the first order between two cubic modifications Pa−3 ↔ Pm−3m was found at about T0 = 360 K. The structural models associated with partially disordered and totally ordered high and low temperature phases, respectively, comply with a large value of phase transition entropy.
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20.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Flerov I. N., Pogoreltsev E. I., Mel'nikova S. V., Gorev M. V., Kartashev A. V., Bogdanov E. V., Molokeev M. S., Laptash N. M.
Заглавие : Structure, physical properties and phase transitions in (NH4)2TiF6×NH4F
Коллективы : European Symposium on Fluorine Chemistry (17; 2013 ; June ; 21-25; Paris, France)
Место публикации : 17th European Symposium on Fluorine Chemistry: Abstracts book. - 2013. - P.37
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