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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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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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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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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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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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    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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10.

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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Держатели документа:
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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