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Anisotropy of piezocaloric effect at ferroelectric phase transitions in ammonium hydrogen sulphate / E. A. Mikhaleva, M. V. Gorev, M. S. Molokeev [et al.] // J. Alloys Compd. - 2020. - Vol. 839. - Ст. 155085, DOI 10.1016/j.jallcom.2020.155085. - Cited References: 31. - The reported study was supported by the Russian Science Foundation (project no. 19-72-00023 ). 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" . - ISSN 0925-8388
Кл.слова (ненормированные):
Piezocaloric effect -- Phase transition -- Ferroelectrics -- Thermal expansion -- High-pressure -- Entropy
Аннотация: The role of anisotropy of the thermal expansion in formation of piezocaloric effect (PCE) near ferroelectric phase transitions in NH4HSO4 was studied. Strong difference in linear baric coefficients and as a result in intensive and extensive PCE associated with the different crystallographic axes was found. PCE giving the main contribution to the barocaloric effect were determined at both phase transitions. Rather strong effect of the lattice dilatation on the tuning of PCE was observed. Comparative analysis of PCE at the phase transitions in different materials showed that NH4HSO4 can be considered as a promising solid-state refrigerant. A hypothetical cooling cycle based on alternate using uniaxial pressure along two axes was considered.

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Держатели документа:
Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk, 660036, Russian Federation
Institute of Engineering Physics and Radioelectronics, Siberian Federal University, Krasnoyarsk, 660074, Russian Federation
Department of Physics, Far Eastern State Transport University, Khabarovsk, 680021, Russian Federation
Astafijev Krasnoyarsk State Pedagogical University, Krasnoyarsk, 660049, Russian Federation

Доп.точки доступа:
Mikhaleva, E. A.; Михалева, Екатерина Андреевна; Gorev, M. V.; Горев, Михаил Васильевич; Molokeev, M. S.; Молокеев, Максим Сергеевич; Kartashev, A. V.; Карташев, Андрей Васильевич; Flerov, I. N.; Флёров, Игорь Николаевич
}
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Anomalous behaviour of thermodynamic properties at successive phase transitions in (NH4)3GeF7 / E. V. Bogdanov [et al.] // J. Solid State Chem. - 2017. - Vol. 256. - P. 162-167, DOI 10.1016/j.jssc.2017.09.010. - Cited References: 23. - The reported study was partially supported by the Russian Foundation for Basic Research, research project no. 15-02-02009 a. . - ISSN 0022-4596
Кл.слова (ненормированные):
Phase transition -- Fluorides -- Heat capacity -- Entropy -- Thermal expansion -- High pressure
Аннотация: Heat capacity, thermal dilatation, susceptibility to hydrostatic pressure and dielectric properties associated with succession of three phase transitions below room temperature in double fluoride salt (NH4)3GeF7 were studied. A possible transformation into the parent Pm-3m cubic phase was not observed up to the decomposition of compound. Nonferroelectric nature of structural distortions was confirmed. The DTA under pressure studies revealed a high temperature stability of two phases: P4/mbm and Pbam. The entropies of the phase transitions agree well with the model of structural distortions. Analysis of the thermal properties associated with the individual phase transitions in the framework of thermodynamic equations has shown a high reliability of the data obtained. © 2017 Elsevier Inc.

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Держатели документа:
Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk, Russian Federation
Institute of Engineering Systems and Energy, Krasnoyarsk State Agrarian University, Krasnoyarsk, Russian Federation
Astafijev Krasnoyarsk State Pedagogical University, Krasnoyarsk, Russian Federation
Institute of Engineering Physics and Radioelectronics, Siberian Federal University, Krasnoyarsk, Russian Federation
Institute of Chemistry, Far Eastern Department of RAS, Vladivostok, Russian Federation

Доп.точки доступа:
Bogdanov, E. V.; Богданов, Евгений Витальевич; Kartashev, A. V.; Карташев, Андрей Васильевич; Pogoreltsev, E. I.; Погорельцев, Евгений Ильич; Gorev, M. V.; Горев, Михаил Васильевич; Laptash, N. M.; Flerov, I. N.; Флёров, Игорь Николаевич
}
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Calorimetric, dilatometric and DTA under pressure studies of the phase transitions in elpasolite (NH4)2KZrF7 / M. V. Gorev, A. V. Kartashev, E. V. Bogdanov [et al.] // J. Fluor. Chem. - 2020. - Vol. 235. - Ст. 109523, DOI 10.1016/j.jfluchem.2020.109523. - 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" . - ISSN 0022-1139
Кл.слова (ненормированные):
Phase transition -- Fluorides -- Heat capacity -- Entropy -- Thermal expansion -- High pressure
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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Держатели документа:
Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk, 660036, Russian Federation
Institute of Engineering Physics and Radioelectronics, Siberian Federal University, Krasnoyarsk, 660074, Russian Federation
Astafijev Krasnoyarsk State Pedagogical University, Krasnoyarsk, 660049, Russian Federation
Institute of Engineering Systems and Energy, Krasnoyarsk State Agrarian University, Krasnoyarsk, 660049, Russian Federation
Institute of Chemistry, Far Eastern Department of RAS, Vladivostok, 690022, Russian Federation

Доп.точки доступа:
Gorev, M. V.; Горев, Михаил Васильевич; Kartashev, A. V.; Карташев, Андрей Васильевич; Bogdanov, E. V.; Богданов, Евгений Витальевич; Flerov, I. N.; Флёров, Игорь Николаевич; Laptash, N. M.
}
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Chemical pressure as an effective tool for tuning the structural disordering and barocaloric efficiency of complex fluorides (NH4)3MF7 (M: Sn, Ti, Ge, Si) / I. N. Flerov, M. V. Gorev, E. V. Bogdanov, N. M. Laptash // J. Phys. D: Appl. Phys. - 2024. - Vol. 57, Is. 17. - Ст. 175301, DOI 10.1088/1361-6463/ad211b. - Cited References: 39. - The study was supported by a Grant from the Russian Science Foundation No. 23-22-00115, https://rscf.ru/project/23-22-00115/ . - ISSN 0022-3727. - ISSN 1361-6463
Кл.слова (ненормированные):
fluorides -- phase transformation -- phase diagram -- entropy -- pressure -- barocaloric effect
Аннотация: Double fluoride salts (NH4)3M4+F7 (M4+: Sn, Ti, Ge, Si) demonstrate a high efficiency of using chemical pressure as a tool for control and tuning structural ordering/disordering, sensitivity to hydrostatic pressure, successions of the phase transitions, etc and, as a result, for purposeful variation within a wide range of parameters of barocaloric effect (BCE). The conventional and inverse BCEs near the triple points were found on the T − p phase diagrams, combination of which can be used to construct original cooling cycle in narrow temperature and pressure ranges. Reconstructive transformation between two cubic phases, Pm3-m ↔ Pa3-, realized in (NH4)3SnF7 at atmospheric pressure and in (NH4)3TiF7 at p ˃ 0.4 GPa are characterized by rather low thermal hysteresis, δT0 = 1 K, and a great entropy change, ΔSBCE = 110–152 J (kg · K)−1, depending on the size of the central atom. At above 300–350 K, a contribution to BCE associated with the regular thermal expansion of the crystal lattice becomes comparable to entropy and temperature changes under pressure in the region of the phase transitions. An analysis of the absolute, relative and integral barocaloric characteristics of (NH4)3M4+F7 compounds showed their high competitiveness with respect to other barocaloric materials considered as promising solid-state refrigerants.

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Держатели документа:
Kirensky Institute of Physics, Federal Research Center KSC SB RAS, 660036 Krasnoyarsk, Russia
Institute of Engineering Physics and Radioelectronics, Siberian Federal University, 660074 Krasnoyarsk, Russia
Institute of Engineering Systems and Energy, Krasnoyarsk State Agrarian University, 660049 Krasnoyarsk, Russia
Institute of Chemistry, Far Eastern Department of RAS, 690022 Vladivostok, Russia

Доп.точки доступа:
Flerov, I. N.; Флёров, Игорь Николаевич; Gorev, M. V.; Горев, Михаил Васильевич; Bogdanov, E. V.; Богданов, Евгений Витальевич; Laptash, N. M.
}
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Gorban, A.
Codon usage trajectories and 7-cluster structure of 143 complete bacterial genornic sequences / A. . Gorban, T. . Popova, A. . Zinovyev // Physica A. - 2005. - Vol. 353. - P. 365-387, DOI 10.1016/j.physa.2005.01.043. - Cited References: 46 . - ISSN 0378-4371

РУБ Physics, Multidisciplinary
Рубрики:
DNA-BASE COMPOSITION
   ASYMMETRIC SUBSTITUTION PATTERNS
   PROTEIN-CODING REGIONS
   MICROBIAL GENOMES
   GENE IDENTIFICATION
   MARKOV-MODELS
   G+C CONTENT
   BIAS
   PREDICTION
   SELECTION
Кл.слова (ненормированные):
genome -- cluster -- codon usage -- correlations -- entropy -- mean field -- Cluster -- Codon usage -- Correlations -- Entropy -- Genome -- Mean field -- Approximation theory -- Correlation methods -- Database systems -- Entropy -- Functions -- Genes -- Mathematical models -- Clusters -- Codon usage -- Genomes -- Mean field -- Bacteria
Аннотация: Three results are presented. First, we prove the existence of a universal 7-cluster structure in all 143 completely sequenced bacterial genomes available in Genbank in August 2004, and explained its properties. The 7-cluster structure is responsible for the main part of sequence heterogeneity in bacterial genomes. In this sense, our 7 clusters is the basic model of bacterial genome sequence. We demonstrated that there are four basic "pure" types of this model, observed in nature: "parallel triangles", "perpendicular triangles", degenerated case and the flower-like type. Second, we answered the question: how big are the position-specific information and the contribution connected with correlations between nucleotide. The accuracy of the mean-field (context-free) approximation is estimated for bacterial genomes. We show that codon us-age of bacterial genomes is a multi-linear function of their genomic G+C-content with high accuracy (more precisely, by two similar functions, one for eubacterial genomes and the other one for archaea). Description of these two codon-usage trajectories is the third result. All 143 cluster animated 3D-scatters are collected in a database and is made available on our web-site: http://www.ihes.fr/similar to zinovyev/7clusters. (c) 2005 Elsevier B.V. All rights reserved.

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Держатели документа:
Univ Leicester, Dept Math, Leicester LE1 7RH, Leics, England
RAS, SB, Inst Computat Modelling, Krasnoyarsk, Russia
Bures Sur Yvette & Bioinformat Serv Inst Curie, Inst Hautes Etudes Sci, Paris, France
ИВМ СО РАН
Department of Mathematics, University of Leicester, Leicester, University Road, Leicester LE1 7RH, United Kingdom
Institute of Computational Modelling, SB RAS, Krasnoyarsk, Russian Federation
Institut des Hautes Etudes Scientifiques, Bures-sur-Yvette and Bioinformatics Service of Institut Curie, Paris, France

Доп.точки доступа:
Popova, T.; Zinovyev, A.
}
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Comparative analysis of elastocaloric and barocaloric effects in single-crystal and ceramic ferroelectric (NH4)2SO4 / E. Mikhaleva, M. Gorev, V. Bondarev [et al.] // Scripta Mater. - 2021. - Vol. 191. - P. 149-154, DOI 10.1016/j.scriptamat.2020.09.030. - Cited References: 47. - The reported study was supported by the Russian Science Foundation (project no. 19-72-00023 ). 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” . - ISSN 1359-6462
Кл.слова (ненормированные):
Polymorphic phase transformation -- Phase diagram -- Order–disorder phenomena -- Entropy -- Caloric effects
Аннотация: We report the influence of anisotropy and texture on elasto(ElCE)- and baro(BCE)-caloric effects in single-crystal and ceramic (NH4)2SO4. Inverse extensive and intensive ElCE in ceramics, (ΔSElCE)cer = 87 J/kg·K; ΔTAD = - 11.6 K), as well as in a single crystal along the ferroelectric axis a, (ΔSElCE)a = 115 J/kg·K; (ΔTAD)a = - 16 K, significantly exceed BCE, ΔSBCE = 75 J/kg·K; ΔTAD = - 9.8 K, even at low pressure ~ 0.3 GPa. Caloric parameters of ammonium sulphate are comparable with those for promising solid-state refrigerants.

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Держатели документа:
Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk, 660036, Russian Federation
Institute of Engineering Physics and Radioelectronics, Siberian Federal University, Krasnoyarsk, 660074, Russian Federation
Institute of Engineering Systems and Energy, Krasnoyarsk State Agrarian University, Krasnoyarsk, 660049, Russian Federation

Доп.точки доступа:
Mikhaleva, E. A.; Михалева, Екатерина Андреевна; Gorev, M. V.; Горев, Михаил Васильевич; Bondarev, V. S.; Бондарев, Виталий Сергеевич; Bogdanov, E. V.; Богданов, Евгений Витальевич; Flerov, I. N.; Флёров, Игорь Николаевич
}
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Gorev, M. V.
Conventional and inverse barocaloric effects around triple points in ferroelastics (NH4)3NbOF6 and (NH4)3TiOF5 / M. V. Gorev, E. V. Bogdanov, I. N. Flerov // Scripta Mater. - 2017. - Vol. 139. - P. 53-57, DOI 10.1016/j.scriptamat.2017.06.022. - Cited References: 17 . - ISSN 1359-6462
Кл.слова (ненормированные):
Barocaloric effect -- Entropy -- Order-disorder phenomena -- Phase diagram -- Polymorphic phase transformation
Аннотация: We report the conventional and inverse barocaloric effect (BCE) in ferroelastics (NH4)3NbOF6 and (NH4)3TiOF5. We found a rich set of the structural phase transitions and triple points on the T − p phase diagrams. Extensive and intensive BCE near some transformations and around triple points in both crystals are outstanding (|∆ SBCE max | = 30–100 J/kg·K; |∆ TAD max | = 4–22 K) and can be achieved at low pressure 0.01–0.60 GPa.

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Держатели документа:
Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk, Russian Federation
Institute of Engineering Physics and Radioelectronics, Siberian Federal University, Krasnoyarsk, Russian Federation
Institute of Engineering Systems and Energy, Krasnoyarsk State Agrarian University, Krasnoyarsk, Russian Federation

Доп.точки доступа:
Bogdanov, E. V.; Богданов, Евгений Витальевич; Flerov, I. N.; Флёров, Игорь Николаевич; Горев, Михаил Васильевич
}
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Conventional and inverse barocaloric effects in ferroelectric NH4HSO4 / M. V. Gorev [et al.] // J. Alloys Compd. - 2019. - Vol. 806. - P. 1047-1051, DOI 10.1016/j.jallcom.2019.07.273. - Cited References: 22 . - ISSN 0925-8388
Кл.слова (ненормированные):
Polymorphic phase transformation -- Phase diagram -- Order–disorder phenomena -- Entropy -- Barocaloric effect
Аннотация: In this study, the conventional and inverse barocaloric effects (BCE) in ferroelectric NH4HSO4 are reported. Maximum extensive and intensive BCE near order–disorder phase transition can be achieved at low pressure p≤0.1 GPa. Large thermal expansion of the crystal lattice plays a very important role in the developing conventional BCE and conversation between BCE of different sign in the narrow temperature range.

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Держатели документа:
Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk, Russian Federation
Institute of Engineering Physics and Radioelectronics, Siberian Federal University, Krasnoyarsk, Russian Federation
Institute of Engineering Systems and Energy, Krasnoyarsk State Agrarian University, Krasnoyarsk, 660049, Russian Federation

Доп.точки доступа:
Gorev, M. V.; Горев, Михаил Васильевич; Mikhaleva, E. A.; Михалева, Екатерина Андреевна; Flerov, I. N.; Флёров, Игорь Николаевич; Bogdanov, E. V.; Богданов, Евгений Витальевич
}
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Direct and indirect studies of the electrocaloric effect in single crystalline ferrielectric (NH4)2SO4 / V. S. Bondarev, E. A. Mikhaleva, M. V. Gorev, I. N. Flerov // J. Alloys Compd. - 2022. - Vol. 892. - Ст. 162130, DOI 10.1016/j.jallcom.2021.162130. - Cited References: 38. - The reported study was supported by the Russian Science Foundation (project no. 19-72-00023) . - ISSN 0925-8388
Кл.слова (ненормированные):
Ferrielectric -- Electrocaloric effect -- Phase transition -- Entropy
Аннотация: The influence of an electric field on the phase transition parameters and the electrocaloric response in ferrielectric (NH4)2SO4 was studied using a universal multifunctional adiabatic calorimeter. The very low sensitivity of the phase transition temperature to the electric field, dT0/dE ≈ 5·10-3 K/(kV/cm), was shown to be the reason for the low maximum value of the intensive electrocaloric effect, ΔTAD, at E = 11 kV/cm: direct and indirect measurements gave the values of 0.01 K and 0.05 K, respectively. However, the extensive electrocaloric response revealed by an analysis of the entropy–temperature–electric field phase diagram was relatively large, with a value of ΔSECE ≈ − 19 J/kg K, due to the significant contribution of a jump in the excess entropy to the total value, δS0/ΔS0 ~ 0.37. An additional irreversible increase in temperature under the electric field was associated with the Joule effect and indicated a significant electrical conductivity of ammonium sulphate.

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Держатели документа:
Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk, 660036, Russian Federation
Institute of Engineering Physics and Radioelectronics, Siberian Federal University, Krasnoyarsk, 660074, Russian Federation

Доп.точки доступа:
Bondarev, V. S.; Бондарев, Виталий Сергеевич; Mikhaleva, E. A.; Михалева, Екатерина Андреевна; Gorev, M. V.; Горев, Михаил Васильевич; Flerov, I. N.; Флёров, Игорь Николаевич
}
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10.

    Disorder and phase transitions in oxyfluoride (NH4)(3)Ta(O-2)(2)F-4 / I. N. Flerov [et al.] // J. Fluor. Chem. - 2011. - Vol. 132, Is. 10. - P. 713-718, DOI 10.1016/j.jfluchem.2011.05.012. - 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] . - ISSN 0022-1139
Рубрики:
HEAT-CAPACITY
   COMPLEXES
   RB2KTIOF5
   FLUORIDES
   CRYOLITE
Кл.слова (ненормированные):
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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Держатели документа:
Russian Acad Sci, LV Kirensky Phys Inst, Siberian Div, Siberian Dept, Krasnoyarsk 660036, Russia
Siberian Fed Univ, Krasnoyarsk 660074, Russia
RAS, Inst Chem, Far Eastern Dept, Vladivostok 690022, Russia

Доп.точки доступа:
Flerov, I. N.; Флёров, Игорь Николаевич; Gorev, M. V.; Горев, Михаил Васильевич; Fokina, V. D.; Фокина, Валентина Дмитриевна; Bovina, A. F.; Бовина, Ася Федоровна; Bogdanov, E. V.; Богданов, Евгений Витальевич; Pogoreltsev, E. I.; Погорельцев, Евгений Ильич; Laptash, N. M.
}
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11.

Bogdanov, E. V.
Effect of deuteration on the barocaloric properties of complex vanadates (NH4)3VOxF6−x (x: 1, 2) / E. V. Bogdanov, M. V. Gorev, I. N. Flerov // Solid State Sci. - 2022. - Vol. 133. - Ст. 107022, DOI 10.1016/j.solidstatesciences.2022.107022. - Cited References: 28 . - ISSN 1293-2558
Кл.слова (ненормированные):
Fluorides -- Phase transition -- Entropy -- Barocaloric effect
Аннотация: We report on the analysis of intensive and extensive barocaloric properties and their sensitivity to deuteration of complex oxyfluorides (NH4)3VOxF6−x (x: 1, 2) undergoing a similar sequence of structural phase transitions. Due to the high sensitivity to hydrostatic pressure and the strong disordering of six-coordinated anionic fluoro-oxygen species, (NH4)3VO2F4 and (ND4)3VO2F4 crystals demonstrate the highest barocaloric efficiency at low pressure, p = 0.1 GPa, during the phase transition from the initial cubic phase: barocaloric coefficients reach large values |ΔSBCE|/p ≈ 400 J/(kg K GPa) and ΔTAD/p ≈ 80 K/GPa. Anionic, [VOF5] → [VO2F4], and cationic, [ND4] → [NH4] substitutions are accompanied by a decrease in the disorder of structural units in the cubic phase, which leads to a decrease in changes in entropy and temperature under pressure. The contribution of thermal expansion of the crystal lattice to the total intensive and extensive barocaloric effects is large and amounts to about 30–40%.

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Держатели документа:
Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk, 660036, Russian Federation
Institute of Engineering Systems and Energy, Krasnoyarsk State Agrarian University, Krasnoyarsk, 660049, Russian Federation
Institute of Engineering Physics and Radioelectronics, Siberian Federal University, Krasnoyarsk, 660074, Russian Federation

Доп.точки доступа:
Gorev, M. V.; Горев, Михаил Васильевич; Flerov, I. N.; Флёров, Игорь Николаевич; Богданов, Евгений Витальевич
}
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12.

Effect of the size of the central atom on the stability of crystalline phases in solid solutions (NH4)3TixSn1-xF7 / E. V. Bogdanov, E. I. Pogoreltsev, M. V. Gorev [et al.] // J. Solid State Chem. - 2023. - Vol. 328. - Ст. 124373, DOI 10.1016/j.jssc.2023.124373. - Cited References: 20. - The study was supported by a grant from the Russian Science Foundation № 23-22-00115, https://rscf.ru/project/23-22-00115/. - X-ray and dilatometric data and SEM images were obtained using the equipment of the Krasnoyarsk Regional Center for Collective Use of the Federal Research Center — Krasnoyarsk Science Center of the Siberian Branch of the Russian Academy of Sciences. We are grateful to Dr. A.V. Shabanov for examination of the SEM images . - ISSN 0022-4596. - ISSN 1095-726X
Кл.слова (ненормированные):
Phase transition -- Fluorides -- Heat capacity -- Entropy -- Thermal expansion -- Birefringence -- Solid solution -- Internal pressure
Аннотация: The effect of a change in internal pressure as a result of partial substitution of the central atom on the realization and stability of the initial and distorted crystalline phases in (NH4)3TixSn1-xF7 solid solutions has been studied. It was found that at a Ti concentration in the range of x = 0.15–0.40, the reconstructive transition Pm-3m ↔ Pa-3 is transformed into a sequence of phase transitions Pm-3m ↔ P4/mbm ↔ P4/mnc ↔ Pa-3. In the (NH4)3Ti0.15Sn0.85F7 solid solution, the first-order phase transition between two cubic phases at T0 = 352 K is characterized by a significant volume jump δ(ΔV/V0) ≈ 1 %, comparable with that in (NH4)3SnF7. An increase of the Ti concentration leads to a strong decrease in the stability of the Pm-3m cubic phase: the first tetragonal P4/mbm phase appears in (NH4)3Ti0.4Sn0.6F7 at T0 = 400 K, which proves the existence of the predicted high-temperature cubic phase in (NH4)3TiF7. In solid solutions, a decrease in birefringence and entropy of phase transitions was observed in comparison with the initial compounds with Sn and Ti as central atoms. The role of critical parameters (unit cell volume, temperature, external pressure) in the formation of cubic and distorted phases is discussed.

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Kirensky Institute of Physics, Federal Research Center KSC SB RAS, 660036, Krasnoyarsk, Russia
Institute of Engineering Systems and Energy, Krasnoyarsk State Agrarian University, 660049, Krasnoyarsk, Russia
Institute of Engineering Physics and Radioelectronics, Siberian Federal University, 660074, Krasnoyarsk, Russia
Institute of Chemistry, Far Eastern Department of RAS, 690022, Vladivostok, Russia

Доп.точки доступа:
Bogdanov, E. V.; Богданов, Евгений Витальевич; Pogoreltsev, E. I.; Погорельцев, Евгений Ильич; Gorev, M. V.; Горев, Михаил Васильевич; Mel'nikova, S. V.; Мельникова, Светлана Владимировна; Molokeev, M. S.; Молокеев, Максим Сергеевич; Laptash, N. M.; Flerov, I. N.; Флёров, Игорь Николаевич
}
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13.

Flerov, I. N.
Entropy and the mechanism of phase transitions in elpasolites / I. N. Flerov, M. V. Gorev // Phys. Solid State. - 2001. - Vol. 43, Is. 1. - P. 127-136, DOI 10.1134/1.1340198. - Cited References: 33 . - ISSN 1063-7834

РУБ Physics, Condensed Matter
Рубрики:
ORDERED PEROVSKITE PB2MGTEO6
   ELASTIC NEUTRON-DIFFRACTION
   THERMODYNAMIC PROPERTIES
   CUBIC PEROVSKITES
   CRYSTAL-STRUCTURE
   HIGH-RESOLUTION
   PB2MGWO6
   CSPBCL3
Аннотация: The phase transitions in series of crystals with the general formulas A(2)BB'X-6 (X = F, Cl, Br, or CN) and Pb2BB'O-6 that belong to the elpasolite family (space group Fm(3) over bar m) are analyzed. The influence of the size and the shape of cations and anions on the entropy and the mechanism of structural distortions is discussed. (C) 2001 MAIK "Nauka/Interperiodica".

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Держатели документа:
Russian Acad Sci, Siberian Div, Kirenskii Inst Phys, Krasnoyarsk 660036, Russia
ИФ СО РАН
Kirenskii Inst. of Physics, Siberian Division, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, 660036, Russian Federation

Доп.точки доступа:
Gorev, M. V.; Горев, Михаил Васильевич; Флёров, Игорь Николаевич
}
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14.

Flerov, I. N.
Entropy of Rb2KB3+F6 (B3+: Se, In, Lu, Er, Ho) ferroelastics and the triple point on T(R(B)(3+)) diagram / I. N. Flerov, M. V. Gorev, V. N. Voronov // Fiz. Tverd. Tela. - 1996. - Vol. 38, Is. 3. - P. 717-727. - Cited References: 26 . - ISSN 0367-3294

РУБ Physics, Condensed Matter
Рубрики:
STRUCTURAL PHASE-TRANSITIONS
RB2KMIIIF6 ELPASOLITES

WOS

Доп.точки доступа:
Gorev, M. V.; Voronov, V. N.
}
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15.

Features of the behavior of the barocaloric effect near ferroelectric phase transition close to the tricritical point / E. A. Mikhaleva, I. N. Flerov, M. V. Gorev [et al.] // Crystals. - 2020. - Vol. 10, Is. 1. - Ст. 51, DOI 10.3390/cryst10010051. - Cited References: 28. - The reported study was supported by the Russian Science Foundation (project no. 19-72-00023) . - ISSN 2073-4352
Кл.слова (ненормированные):
polymorphic phase transformation -- phase diagram -- order-disorder phenomena -- entropy -- barocaloric effect
Аннотация: A detailed study of the effect of temperature and pressure on heat capacity, entropy and hysteresis phenomena near the ferroelectric phase transition in ammonium sulfate (AS) was performed. An analysis of experimental results within the framework of the phenomenological theory showed that taking into account the temperature-dependent part of the anomalous entropy leads to a significant increase in the barocaloric effect (BCE). The maximum values of extensive and intensive BCE near the tricritical point are outstanding: ΔSmaxBCE≈85 J/kgK, ΔTmaxAD≈12 K and can be achieved at low pressure ∼0.5 GPa.

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Держатели документа:
Kirensky Institute of Physics, Federal Research Center KSC Siberian Branch, Russian Academy of Sciences, 660036 Krasnoyarsk, Russia
Institute of Engineering Physics and Radioelectronics, Siberian Federal University, 660074 Krasnoyarsk, Russia
Institute of Engineering Systems and Energy, Krasnoyarsk State Agrarian University, 660049 Krasnoyarsk, Russia

Доп.точки доступа:
Mikhaleva, E. A.; Михалева, Екатерина Андреевна; Flerov, I. N.; Флёров, Игорь Николаевич; Gorev, M. V.; Горев, Михаил Васильевич; Bondarev, I. A.; Бондарев, Илья Александрович; Bogdanov, E. V.; Богданов, Евгений Витальевич
}
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16.

Heat capacity and thermal expansion of nanosized ferroelectric (NH4)2SO4 embedded in borosilicate glasses / E. A. Mikhaleva, M. V. Gorev, V. S. Bondarev [et al.] // J. Non-Cryst. Solids. - 2022. - Vol. 597. - Ст. 121935, DOI 10.1016/j.jnoncrysol.2022.121935. - Cited References: 29. - The authors are grateful to Dr. Ewa Rysiakiewicz-Pasek (Wroclaw University of Science and Technology, Poland) for the preparation and characterization of borosilicate glasses. 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” . - ISSN 0022-3093
Кл.слова (ненормированные):
Nanocomposite -- Ferroelectrics -- Phase transition -- Thermal expansion -- Entropy
Аннотация: The thermal properties of nanocomposites obtained by incorporating a ferroelectric (NH4)2SO4 (AS) into porous glasses (PG) was studied for the first time. X-ray diffraction studies showed a strong increase in the ratio of the size of nanocrystallites grown in glass matrices to pore size, dcryst/ dpore = 0.47→1.50→5.00, with a decrease in dpore = 320→46→7 nm. Calorimetric and dilatometric measurements showed a change from a first-order phase transition in AS single crystal to a second-order transformation in AS nanocrystallites. A restricted geometry also led to a significant decrease in the anomalous entropy in AS+PG samples compared to AS (J/mol∙K): 17.7 (AS)→12.4 (AS+PG320)→10.4 (AS+PG46)→8.1 (AS+PG7). A discussion of the nontrivial behavior of the phase transition temperature in embedded AS was carried out using the degree of PG filling, the ratio dcryst/dpore, texture, and the volumetric and linear baric coefficients for the bulk AS.

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Держатели документа:
Federal Research Center KSC SB RAS, Kirensky Institute of Physics, Krasnoyarsk, 660036, Russian Federation
Siberian Federal University, Krasnoyarsk, 660074, Russian Federation
Federal Research Center "Krasnoyarsk Science Center of the Siberian Branch of the Russian Academy of Sciences, Krasnoyarsk, 660036, Russian Federation
Ioffe Physico-Technical Institute, RAS, St.-Petersburg, 194021, Russian Federation

Доп.точки доступа:
Mikhaleva, E. A.; Михалева, Екатерина Андреевна; Gorev, M. V.; Горев, Михаил Васильевич; Bondarev, V. S.; Бондарев, Виталий Сергеевич; Molokeev, M. S.; Молокеев, Максим Сергеевич; Zaitsev, A. I.; Зайцев, Александр Иванович; Nemtsev, I. V.; Fokin, A. V.; Flerov, I. N.; Флёров, Игорь Николаевич
}
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17.

Heat capacity of a mixed-valence manganese oxide Pb(3)Mn(7)O(15) / N. V. Volkov [et al.] // J. Phys.: Condens. Matter. - 2008. - Vol. 20, Is. 44. - Ст. 445214, DOI 10.1088/0953-8984/20/44/445214. - Cited References: 11. - This study was supported by the INTAS (project No 061000013-9002), the Division of Physical Sciences of RAS, program `Spin-dependent Effects in Solids and Spintronics' (project No. 2.4.2 of SB RAS), the President of the Russian Federation, grant for Support of Leading Scientific Schools (project No. NSh-1011.2008.2), KRSF-RFBR `Enisey2007', project No. 07-02-96801-a, and the Siberian Branch of RAS, Integration project No. 3.7. . - ISSN 0953-8984

РУБ Physics, Condensed Matter

Кл.слова (ненормированные):
Antiferromagnetism -- Crystallography -- Entropy -- Lead alloys -- Magnetic materials -- Magnetism -- Manganese -- Manganese compounds -- Powders -- Single crystals -- Specific heat -- Spin dynamics -- Antiferromagnetic orders -- Charge localizations -- Entropy losses -- Excess heat capacities -- Experimental datums -- Heat capacities -- Magnetic contributions -- Magnetic orders -- Magnetic states -- Magnetic subsystems -- Magnetic transitions -- Manganese oxides -- Nonmagnetic -- Spin systems -- Temperature curves -- Temperature dependences -- Temperature intervals -- Temperature ranges -- Manganese alloys
Аннотация: We present the results of a heat capacity study of Pb(3)Mn(7)O(15) single crystals with approximately equal concentrations of Mn(3+) and Mn(4+) ions. In the temperature interval between 210 and 260 K, an excess heat capacity of nonmagnetic origin, most likely associated with the process of charge localization, has been observed. Also, three pronounced anomalies corresponding to the changes in a magnetic subsystem of the crystal have been observed in the temperature dependence of the heat capacity. A broad hump near 150 K is related to the formation of a short-range magnetic order. This process of short-range ordering is rather prominent, considering the appreciable value of the entropy loss accompanying the change in the magnetic state. A clear lambda-shaped peak at 70 K marks the onset of a long-range antiferromagnetic order. Another anomalous contribution to the heat capacity of magnetic origin has been revealed at temperatures below 20 K. This contribution is associated with a magnetic transition of an unknown nature, which is also clearly evident in magnetization versus temperature curves. The total magnetic contribution to the entropy deduced from the actual experimental data over the entire temperature range is much smaller than is expected for a completely ordered Mn spin system in the crystal. We suggest several possible reasons that may account for this `missing' entropy.

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Держатели документа:
[Volkov, N. V.
Sablina, K. A.
Eremin, E. V.
Flerov, I. N.
Kartashev, A.] RAS, SB, LV Kirensky Phys Inst, Krasnoyarsk 660036, Russia
[Volkov, N. V.
Flerov, I. N.] Siberian Fed Univ, Dept Phys, Krasnoyarsk 660041, Russia
[Boeni, P.] Tech Univ Munich, Dept Phys E21, D-85747 Garching, Germany
[Shah, V. R.] Indiana Univ, Dept Phys, Bloomington, IN 47405 USA
[Rasch, J. C. E.
Boehm, M.] Inst Max Von Laue Paul Langevin, F-38042 Grenoble 9, France
[Rasch, J. C. E.
Schefer, J.] Swiss Fed Inst Technol, Neutron Scattering Lab, CH-5232 Villigen, Switzerland
[Rasch, J. C. E.
Schefer, J.] Paul Scherrer Inst, CH-5232 Villigen, Switzerland
ИФ СО РАН
Kirensky Institute of Physics, SB, RAS, 660036 Krasnoyarsk, Russian Federation
Department of Physics, Siberian Federal University, 660041 Krasnoyarsk, Russian Federation
Physics Department E21, Technical University of Munich, D-85747 Garching, Germany
Physics Department, Indiana University, Bloomington, IN 47405, United States
Institut Laue-Langevin, 6 rue Jules Horowitz, 38042 Grenoble, Cedex 9, France
Laboratory for Neutron Scattering, ETH Zurich, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland

Доп.точки доступа:
Volkov, N. V.; Волков, Никита Валентинович; Sablina, K. A.; Саблина, Клара Александровна; Eremin, E. V.; Еремин, Евгений Владимирович; Boni, P.; Shah, V. R.; Flerov, I. N.; Флёров, Игорь Николаевич; Kartashev, A.; Rasch, JCE; Boehm, M.; Schefer, J.
}
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18.

Heat capacity, entropy, dielectric properties and T–p phase diagram of (NH4)3TiF7 / E. I. Pogoreltsev [et al.] // J. Fluor. Chem. - 2014. - Vol. 168. - P. 247-250, DOI 10.1016/j.jfluchem.2014.10.016. - 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). . - ISSN 0022-1139. - ISSN 1873-3328

РУБ Chemistry, Inorganic & Nuclear + Chemistry, Organic
Рубрики:
CRYSTAL-STRUCTURE
   TRANSITIONS
   FLUORIDES
   NH4F
Кл.слова (ненормированные):
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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Держатели документа:
RAS, Siberian Dept, LV Kirensky Phys Inst, Krasnoyarsk 660036, Russia
Siberian Fed Univ, Krasnoyarsk 660074, Russia
Krasnoyarsk State Agr Univ, Krasnoyarsk 660049, Russia
Russian Acad Sci, Far Eastern Dept, Inst Chem, Vladivostok 690022, Russia

Доп.точки доступа:
Pogoreltsev, E. I.; Погорельцев, Евгений Ильич; Flerov, I. N.; Флёров, Игорь Николаевич; Kartashev, A. V.; Карташев, Андрей Васильевич; Bogdanov, E. V.; Богданов, Евгений Витальевич; Laptash, N. M.; 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]
}
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19.

Heat capacity, thermal expansion and sensitivity to hydrostatic pressure of (NH 4 ) 3 SiF 7 at successive structural phase transitions / E. V. Bogdanov [et al.] // J. Solid State Chem. - 2019. - Vol. 276. - P. 152-158, DOI 10.1016/j.jssc.2019.04.029. - Cited References: 20 . - ISSN 0022-4596
Кл.слова (ненормированные):
Phase transition -- Fluorides -- Heat capacity -- Entropy -- Thermal expansion -- High pressure
Аннотация: Heat capacity, thermal dilatation, permittivity and sensitivity to external pressure of (NH4)3SiF 7 were studied. Due to the absence of cubic phases Pm3¯m and Pa3¯, a strong decrease in the total entropy change ∑ΔSi =19 J/mol K associated with four successive transformations P4/mbm↔Pbam↔P2 1 /c11↔P1¯↔P12 1 /c1 was found in silicate in comparison with other double fluoride salts (NH4)3MeF7 (Me: Ge, Ti, Sn) Using analysis of the excess heat capacity in the framework of the thermodynamic theory, the entropies associated with each individual phase transition were determined. In accordance with the entropic parameters, the complete ordering of the structural elements occurs in the monoclinic phase P21/c11. Further change in symmetry is associated with small entropy changes which prove insignificant displacement of structural units. A T−p phase diagram was constructed and good agreement was found between measured and calculated baric coefficients. © 2019 Elsevier Inc.

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Держатели документа:
Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk, Russian Federation
Institute of Engineering Systems and Energy, Krasnoyarsk State Agrarian University, Krasnoyarsk, 660049, Russian Federation
Institute of Engineering Physics and Radioelectronics, Siberian Federal University, Krasnoyarsk, Russian Federation
Astafijev Krasnoyarsk State Pedagogical University, Krasnoyarsk, 660049, Russian Federation
Institute of Chemistry, Far Eastern Department of RAS, Vladivostok, 690022, Russian Federation

Доп.точки доступа:
Bogdanov, E. V.; Богданов, Евгений Витальевич; Pogoreltsev, E. I.; Погорельцев, Евгений Ильич; Gorev, M. V.; Горев, Михаил Васильевич; Kartashev, A. V.; Карташев, Андрей Васильевич; Laptash, N. M.; Flerov, I. N.; Флеров, Игорь Николаевич
}
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20.

    Investigation of thermal properties and structure of complex fluoride K3ZrF7 / M. V. Gorev, M. S. Molokeev, A. V. Kartashev [et al.] // J. Fluor. Chem. - 2021. - Vol. 241. - Ст. 109677, DOI 10.1016/j.jfluchem.2020.109677. - 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" . - ISSN 0022-1139
   Перевод заглавия: Исследование теплофизических свойств и структуры комплексного фторида K3ZrF7
Кл.слова (ненормированные):
Phase transition -- Fluorides -- Structure -- Heat capacity -- Entropy -- Thermal expansion
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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Держатели документа:
Kirensky Institute of Physics, Federal Research Center KSC Siberian Branch, Russian Academy of Sciences, Krasnoyarsk, 660036, Russian Federation
Siberian Federal University, Krasnoyarsk, 660074, Russian Federation
Institute of Chemistry, Far Eastern Department of RAS, Vladivostok, 690022, Russian Federation

Доп.точки доступа:
Gorev, M. V.; Горев, Михаил Васильевич; Molokeev, M. S.; Молокеев, Максим Сергеевич; Kartashev, A. V.; Карташев, Андрей Васильевич; Pogoreltsev, E. I.; Погорельцев, Евгений Ильич; Mel'nikova, S. V.; Мельникова, Светлана Владимировна; Laptash, N. M.; Flerov, I. N.; Флёров, Игорь Николаевич
}
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