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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mel'nikova S. V., Laptash N. M., Gorev M. V., Pogoreltsev E. I.
Заглавие : Mixed-valence hydrated iron fluoridotitanate: synthesis, optics and calorimetry
Место публикации : J. Phys. Chem. Solids. - 2020. - Vol. 142. - Ст.109444. - ISSN 00223697 (ISSN), DOI 10.1016/j.jpcs.2020.109444
Примечания : Cited References: 35
Аннотация: Mixed-valence hydrated fluoridotitanate with idealized formula FeTiF6·6H2O is the main product of fluoride processing of natural mineral ilmenite with hydrofluoric acid. Its single crystals were grown and optical and calorimetric experiments were carried out in the temperature range 200–350 K. Charge re-distribution, Fe2+Ti4+ to Fe3+Ti3+, in the compound studied was evident in XPS spectra. A first order ferroelastic phase transition occurs at temperatures T0↓ = 271.5 K, T0↑ = 274 ÷ 275.5 K with the symmetry change P3‾↔ P1‾. The structural transformation is accompanied by the appearance of a very weak optical anisotropy in the slice (001), a small anomaly of the heat capacity (ΔS = 1.5 J/mol K = 0.2R), and positive baric coefficients dT0/dp ≈ 30 ± 10 K/GPa.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Denisova L. T., Molokeev M. S., Irtyugo L. A., Beletskii V. V., Kargin, Yu. F., Denisov V. M.
Заглавие : Synthesis, structure, and thermophysical properties of EuGaGe2O7
Место публикации : Inorg. Mater. - 2020. - Vol. 56, Is. 8. - P.854-858. - ISSN 0020-1685, DOI 10.1134/S002016852008004X. - ISSN 1608-3172(eISSN)
Примечания : Cited References: 18
Предметные рубрики: TEMPERATURE HEAT-CAPACITY
THERMODYNAMIC PROPERTIES
CRYSTAL-STRUCTURE
Аннотация: The europium gallium germanate EuGaGe2O7 has been prepared by solid-state reaction in air in the temperature range 1273–1473 K using a stoichiometric mixture of Eu2O3, Ga2O3, and GeO2. Its crystal structure has been determined by X-ray diffraction (sp. gr. P21/c, a = 7.1693(7) Å, b = 6.57008(6) Å, c = 12.7699(1) Å, β = 117.4522(5)°, V = 533.768(8) Å3). The heat capacity of polycrystalline samples has been determined by differential scanning calorimetry in the temperature range 350–1053 K and the experimental data have been used to calculate the thermodynamic properties (enthalpy increment, entropy change, and reduced Gibbs energy change) of EuGaGe2O7.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Shtykova M. A., Molokeev M. S., Zakharov B. A., Selezneva N. V., Aleksandrovsky A. S., Bubnova R. S., Kamaev D. N., Gubin A. A., Habibullayev N. N., Matigorov A. V., Boldyreva E. V., Andreev O. V.
Заглавие : Structure and properties of phases in the Cu2-ХSe-Sb2Se3 system. The Cu2-XSe-Sb2Se3 phase diagram
Место публикации : J. Alloys Compd. - 2022. - Vol. 906. - Ст.164384. - ISSN 09258388 (ISSN), DOI 10.1016/j.jallcom.2022.164384
Примечания : Cited References: 111. - The research was supported for R.S. Bubnova by the Ministry of Science and Higher Education of the Russian Federation within the scientific tasks of the Institute of Silicate chemistry (Russian Academy of Sciences) [project number 0097-2019-0013]. The equipment of Research and Education Center "Molecular design and ecologically safe technologies" (Novosibirsk State University) was used for single-crystal X-ray diffraction experiments. BAZ and EVB acknowledge support by the Ministry of Science and Higher Education, project AAAA-A21-121011390011-4
Аннотация: The phase diagram of the Cu2−XSe-Sb2Se3 system is revisited to clarify ambiguity/disagreement in previously reported data. Ternary Cu3SbSe3 and CuSbSe2 compounds were obtained. In order to confirm that the phases have been identified correctly, crystal structures were solved, and the energy band gaps measured. For the sample containing 75 mol% Sb2Se3 and 25 mol% Cu1.995Se the temperature range of the stability of the high-temperature CuSb3Se5 phase was determined for the first time. This phase is formed at 445 °С, decomposes following a peritectic reaction at 527 °С, and can be quenched. A high-temperature X-ray diffraction study of a sample containing 75 mol% Sb2Se3 and 25 mol% Cu2Se allowed us to measure the thermal expansion of the CuSbSe2 and Sb2Se3 phases present in the sample. The anisotropy of thermal expansion of CuSbSe2 is similar to that of As2S3 (orpiment); thermal expansion of Sb2Se3 is similar to that of AsS (realgar). The 6 balance equations of the invariant phase transformations involving all the ternary compounds existing in the Cu2−XSe-Sb2Se3 system were suggested for the first time. The temperature and the enthalpies of all these transformations were measured. A phase diagram of the Cu2−XSe-Sb2Se3 system was found for the first time in all the range of concentrations at temperatures from ambient to the complete melting. This diagram takes into consideration the phase equilibria that involve all the ternary compounds that are possible in this system. The liquidus of the Cu2−XSe-Sb2Se3 system was calculated according to Redlich-Kister equation; it agrees with the experimental data within 1–17 °С.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Bogdanov E. V., Pogoreltsev E. I.
Заглавие : Calorimetric study of the fluoro-oxygen crystal (ND4)2MoO2F4
Коллективы : International conference on thermal analysis and calorimetry in Russia, Международная конференция по термическому анализу и калориметрии в России, Институт общей и неорганической химии им. Н.С. Курнакова РАН, Санкт-Петербургский политехнический университет им. Петра Великого
Место публикации : Proc. of int. conf. on therm. analys. and calorim. in Russia (RTAC-2016). - 2016. - Vol. I. - P.181. - ISBN 978-5-7422-5447-8
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Миронов, Валерий Леонидович, Каравайский, Андрей Юрьевич, Лукин, Юрий Иванович, Погорельцев, Евгений Ильич
Заглавие : Диэлектрический метод измерения скрытой теплоты плавления льда при оттаивании мерзлой почвы
Место публикации : Журн. радиоэлектрон.: электронный журнал. - 2018. - № 12. - Ст.14. - ISSN 1684-1719, DOI 10.30898/1684-1719.2018.12.14
Примечания : Библиогр.: 14
Ключевые слова (''Своб.индексиров.''): диэлектрическая модель--диэлектрическая проницаемость--мерзлые почвы--незамерзшая вода--незамерзающая вода--связанная вода--фазовые переходы--дифференциальная сканирующая калориметрия--dielectric model--dielectric constant--frozen soil--unfrozen water--nonfreezable water--bound water--phase transitions--differential scanning calorimetry
Аннотация: Проведены экспериментальные исследования изменения массы незамерзшей воды, содержащейся в мерзлой Nа-бентонитовой глине в диапазоне температур от -30 до 0 °C и диапазоне массовых влажностей от 0 до 1 г/г с помощью диэлектрического метода. Предложен калориметрический метод измерения удельной скрытой теплоты плавления льда в связанную и несвязанную воду при нагревании мерзлой почвы. Предложен метод измерения скрытой теплоты плавления льда в мерзлой почве в процессе нагревания методом диэлектрических измерений. С целью обоснования предложенной методики проведено сравнение скрытой теплоты плавления льда при нагревании бентонитовой глины, полученной методом дифференциальной сканирующей калориметрии (ДСК), с рассчитанной с помощью диэлектрического метода.Experimental studies of the change in the mass of unfrozen water contained in frozen Na-bentonite clay in the temperature range from -30 to 0 °C and a gravimetric moistures range from 0 to 1 g/g have been carried out by the dielectric method. The calorimetric method is proposed for measuring the specific latent heat of fusion of ice into bound and unbound water when the frozen soil is heated. The method of dielectric measurements is proposed for measuring the latent heat of fusion of ice in frozen soils during heating. In order to substantiate the proposed technique, the latent heat of fusion of ice in frozen bentonite clay measured by the differential scanning calorimetry during heating was compared with this value obtained by the dielectric method.
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Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Flerov I. N., Gorev M. V., Bogdanov E. V.
Заглавие : Conversial and inversial barocaloric effects around triple points in ferroelastics (NH4)3NbOF6 and (NH4)3TiOF5
Коллективы : Journale of Thermal Analysis and Calorimetry Conference, Joint Czech-Hungarian-Polish-Slovakian) Thermoanalytical Conference
Место публикации : 2nd Journale of Thermal analysis and calorimetry conference: book of abstracts. - 2019. - P.489-490. - ISBN 978-963-454-416-6
Примечания : Cited References:. - The reported study was funded by RFBR according to the research project No 18-02-00269
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fokina V. D., Gorev M. V., Kocharova A. G., Flerov I. N., Pogoreltsev E.I.
Заглавие : Phase transitions and thermodynamic properties of (NH4)(3)VO2F4 cryolite
Место публикации : Solid State Sci. - 2009. - Vol. 11, Is. 4. - P.836-840. - ISSN 1293-2558, DOI 10.1016/j.solidstatesciences.2008.11.004
Примечания : Cited Reference Count: 17. - Гранты: The authors are grateful to Dr. SM. Mel'nikova for the permission to use the unpublished results.; This work was supported by the Russian Foundation for Basic Research (project 06-02-16102).Финансирующая организация: Russian Foundation for Basic Research [06-02-16102]
Предметные рубрики: PEROVSKITE-LIKE OXYFLUORIDES
(NH4)(3)TIOF5
CS
(NH4)(3)WO3F3
DIFFRACTION
(NH4)3VO2F4
ELPASOLITE
METALS
RB
Ключевые слова (''Своб.индексиров.''): oxyfluorides--phase transition--calorimetry--phase diagram--ferroelectricity--calorimetry--ferroelectricity--oxyfluorides--phase diagram--phase transition--calorimetry--ferroelectricity--halide minerals--phase diagrams--sugar (sucrose)--thermodynamic properties--calorimetric measurements--cubic phase--first-order phase transitions--heat capacities--oxyfluorides--phase transition temperatures--pressure dependences--structural transformations--temperature ranges--phase transitions
Аннотация: Calorimetric measurements performed in a wide temperature range on (NH4)(3)VO2F4 have shown the presence of four heat capacity anomalies at T-1 = 438 K, T-2 = 244 K, T-3 = 210.2 K, T-4 = 205.1 K associated with the first order phase transitions. In accordance with the permittivity behavior, the structural transformations are of nonferroelectric nature. Pressure dependence of the phase transition temperatures has been studied by DTA under pressure. The entropy of phase transitions is analyzed mainly in the framework of the orientational disordering of NH4+ and VO2F43- ions in a cubic phase. (C) 2008 Elsevier Masson SAS. All rights reserved.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Moiseenko E. T., Yumashev V. V., Altunin R. R., Solovyov L. A., Volochaev M. N., Belousov O. V., Zharkov S. M.
Заглавие : Thermokinetic study of intermetallic phase formation in an Al/Cu multilayer thin film system
Место публикации : Materialia. - 2023. - Vol. 28. - Ст.101747. - ISSN 25891529 (eISSN), DOI 10.1016/j.mtla.2023.101747
Примечания : Cited References: 53. - This work was supported by the Russian Science Foundation under grant # 22-13-00313
Аннотация: The solid-state reaction process in a multilayer thin film system (Al/Cu)50 has experimentally been studied using the methods of simultaneous thermal analysis (STA) and in situ electron diffraction. A detailed kinetic analysis of the phase formation processes during the solid-state reaction has shown that the observed solid-state transformations can be described by a statistically significant kinetic model where each stage corresponds to the reaction of the n-th order with autocatalysis. The low-temperature stage has been demonstrated to be attributable to the formation of the θ-Al2Cu phase, with the medium-temperature and high-temperature ones corresponding to the α2-AlCu3 and γ1-Al4Cu9 phases, respectively. The kinetic parameters for the formation of the phases θ-Al2Cu, α2-AlCu3 and γ1-Al4Cu9 have been determined. It has been shown that the kinetic model describing the solid-state reaction in the Al–Cu multilayer thin film system is in best agreement with the experimental data in the case of a competition between the formation stages of the α2-AlCu3 and γ1-Al4Cu9 phases.
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Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Yurev I. O., Aleksandrovsky A. S., Kamaev D. N., Polkovnikov A. A., Grigorchenko V. M., Yarovenko A. A., Zelenaya A. E., Parfenova M. D., Andreev O. V.
Заглавие : The Sm2S3-X-SmS-Sm2O2S refractory system: thermal analysis, phase diagram, and properties of the phases
Колич.характеристики :17 с
Место публикации : J. Therm. Anal. Calorim. - 2024. - Vol. 149, Is. 5. - P.2057-2073. - ISSN 13886150 (ISSN), DOI 10.1007/s10973-023-12792-z. - ISSN 15882926 (eISSN)
Примечания : Cited References: 90. - The authors thank Prof. P.P. Fedorov, Chief Researcher of Prokhorov Institute of General Physics, Russian Academy of Sciences, for scientific advices. The authors thank N.I. Lozhkin, engineer of the Department of Inorganic and Physical Chemistry, Tyumen State University for the technical support of the visual thermal analysis setup. The authors thank N.A. Shulaev, research engineer of the Center for Nature-Inspired Engineering, Tyumen State University, for determining the elemental composition of samples by scanning electron microscopy. The authors thank I.V. Palamarchuk, research engineer of the Center for Collective Use "Rational Nature Management and Physical and Chemical Research" of the Tyumen State University, for measuring the diffuse reflectance spectra. The authors thank Doctor of Philology O.V. Trofimova, Professor at the Institute of Social Sciences and Humanities of the Tyumen State University, for her advices on academic writingThis study was funded by the Russian Science Foundation, Project No. 23–23-00488 “Search for EMF generation conditions in gradient ceramics of samarium monosulfide (SmS)”
Аннотация: Samarium monosulfide, a strain gauge and barometric material, exists in equilibrium with Sm3S4 and Sm2O2S in the S-Sm–O system. Therefore, studying phase equilibria in the refractory Sm2S3-X-SmS-Sm2O2S system is a scientifically interesting task. In this system, 49 samples were synthesized and studied by powder XRD, differential scanning calorimetry, visual thermal analysis, and microstructural analysis. Melting points of Sm3S4, SmS, and Sm2O2S compounds were determined. Eutectic diagrams of Sm3S4-Sm2O2S, SmS-Sm2O2S, SmS-Sm3S4 systems were constructed. Temperatures and compositions of the binary eutectic points were determined. Fusion enthalpies for Sm3S4, SmS, and Sm2O2S phases were estimated using the Schröder–Le Chatelier equation. The liquidus lines were calculated using second-degree polynomials and Redlich–Kister model. Coordinates of the ternary eutectic point in the Sm3S4-SmS-Sm2O2S system were calculated using the cutting-plane method and the Scheffé method. The calculated compositions of ternary eutectic points were averaged at one most probable point, in accordance with the data on the samples microstructure. The experimental temperature of the ternary eutectic point coincides with the calculated values within the margin of error. Positions of eutectic valleys and approximate positions of isotherms in the system were established. Thermodynamic parameters of the α-Sm2S3 → γ-Sm2S3 polymorphic transition and the dependence of the Sm2S3-X composition on heat treatment conditions were determined. According to the scanning electron microscopy data, the approximate composition of the crystallized from the melt Sm2S3 sample is Sm2S2.95. The Sm10S14O phase decomposes at 1470 ± 15 °C in the course of a solid-phase reaction. The phase diagram of the Sm2S3-X-Sm2O2S system was revisited. Optical band gaps of Sm10S14O and Sm2O2S phases were determined. The Sm10S14O compound was optically characterized for the first time; its direct and indirect optical bandgaps were found equal to 2.48 and 2.37 eV, respectively. The determined direct and indirect optical bandgaps of Sm2O2S (4.4 eV and 3.95 eV, respectively) agree with the earlier measurements, thus confirming the accuracy of the chosen synthesis procedures.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Volkova E. A., Platunov M. S., Antipin A. M., Alpanova R. R., Dubrovskiy A. A., Pyastolova Yu. V., Podobraznyh A. D., Kosorukov V. L., Koporulina E. V., Maltsev V. V.
Заглавие : Synthesis, structure and magnetic properties of monoclinic lanthanum-chromium borate LaCr3(BO3)4
Колич.характеристики :9 с
Место публикации : J. Alloys Compd. - 2024. - Vol. 994. - Ст.174683. - ISSN 0925-8388, DOI 10.1016/j.jallcom.2024.174683. - ISSN 1873-4669
Примечания : Cited References: 38. - Single crystal X-ray analysis was carried out within the State assignment NRC "Kurchatov institute" (research contribution of A.M.A.). The research contribution of M.S.P. was partially supported by the Ministry of Science and Higher Education of the Russian Federation within the governmental assignment for Synchrotron radiation facility "SKIF", Boreskov Institute of Catalysis (project FWUR-2024–0040)
Аннотация: Single crystals of LaCr3(BO3)4 were synthesized through spontaneous nucleation from a K2Mo3O10 flux melt. The crystal structure was determined using single-crystal X-ray diffraction (XRD) at temperatures of 293 K and 85 K. LaCr-borate crystallizes in the monoclinic C2/c space group with unit cell parameters a = 7.47980(5) Å, b = 9.55180(7) Å, c = 11.48330(8) Å, β= 104.0060(6)°, V = 796.04(1) Å3 (for C1, T = 293 K), and a = 7.47380(5) Å, b = 9.55520(7) Å, c = 11.47100(8) Å, β = 103.9330(6)°, V = 795.08(1) Å3 (for C2, T = 85 K), each with Z = 4. The temperature dependence of the unit cell parameters, including the monoclinic angle (β) and the unit cell volume (V), was investigated over the range of 85–293 K. No structural phase transitions were observed in the low-temperature region down to 85 K. Differential scanning calorimetry (DSC) measurements revealed no high-temperature phase transitions between 50 and 1350°C. Infrared (IR) spectroscopy confirmed the monoclinic structure of LaCr3(BO3)4 crystals, revealing characteristic absorption bands, including the lowest frequency mode associated with the translational vibrations of the La3+ ion.
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11.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Denisova L. T., Molokeev M. S., Galiakhmetova N. A., Denisov V. M., Belousova N. V.
Заглавие : Heat capacity and thermodynamic properties of germanates CaR2Ge3O10 (R = Pr, Nd) in the region of 320–1000 K
Место публикации : Russ. J. Phys. Chem. A. - 2022. - Vol. 96, Is. 5. - P.913-917. - ISSN 00360244 (ISSN), DOI 10.1134/S0036024422050077
Примечания : Cited References: 30. - The authors are grateful to the Krasnoyarsk Regional Shared Resource Center of the Krasnoyarsk Science Center. This work was performed as part of a State Task for Siberian Federal University, project no. FSRZ-2020-0013
Аннотация: Sequential annealing of stoichiometric mixtures of CaCO3, Pr6O11(Nd2O3), and GeO2 in air at 1423–1473 K yields germanates CaPr2Ge3O10 and CaNd2Ge3O10. Their crystal structure is refined via X-ray diffraction. The high-temperature heat capacity (320–1000 K) is measured by means of differential scanning calorimetry. The thermodynamic properties of germanates are calculated using experimental dependences Cp = f(T).
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12.

Вид документа : Статья из журнала
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Автор(ы) : Gorev M. V., Bondarev V. S., Flerov I. N., Bormanis K., Birks E.
Заглавие : T − E phase diagrams and electrocaloric effect in PNN-PT solid solutions
Место публикации : J. Alloys Compd. - 2022. - Vol. 927. - Ст.167032. - ISSN 09258388 (ISSN), DOI 10.1016/j.jallcom.2022.167032
Примечания : Cited References: 40. - The authors are thankful to Dr. Anna Kalvane (Institute of Solid State Physics, University of Latvia) for preparation and characterization of the samples. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors
Аннотация: Using the sixth-order free energy expansion of the Landay thermodynamic potential, T − E phase diagrams and the electrocaloric effect (ECE) in solid solutions (1-x)Pb(Ni1∕3Nb2∕3)O3-xPbTiO3 (PNN-PT) were studied under an electric field along the crystallographic directions [001], [101] and [111]. The composition of the samples, temperature range, as well as magnitude and direction of the electric field significantly affect the sequence of phase transitions, stability of various crystalline phases and electrocaloric properties. Direct measurements of the intensive ECE in the 0.8PNN-0.2PT compound were carried out by the method of adiabatic calorimetry at electric field strength E = 6 kV/cm. The large electrocaloric coefficient ΔT∕ΔE = 10 μK ⋅ cm/kV indicates that this compound and other PNN-PT solutions are promising for application as solid-state refrigerants.
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13.

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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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Gorev M., Bondarev V., Sciau P., Savariault J. M.
Заглавие : Heat capacity study of relaxors BaTi0.65Zr0.35O3 and BaTi0.60Zr0.40O3
Разночтения заглавия :авие SCOPUS: Heat capacity study of relaxors BaTi0.65Zr0.35O 3 and BaTi0.60Zr0.40O3
Место публикации : J. Phys.: Condens. Matter: IOP PUBLISHING LTD, 2006. - Vol. 18, Is. 17. - P.4407-4416. - ISSN 0953-8984, DOI 10.1088/0953-8984/18/17/026
Примечания : Cited References: 21
Предметные рубрики: CERAMICS
BA(TI1-XZRX)O-3
BATIO3
Ключевые слова (''Своб.индексиров.''): calorimetry--composition--data reduction--lead compounds--mathematical models--permittivity--specific heat--adiabatic calorimetry--burns temperature--diffuse anomalies--barium compounds
Аннотация: The heat capacity of two relaxors BaTi(1-x)ZrxO(3) (x = 0.35, 0.40) was measured using adiabatic calorimetry in the temperature range 100-360 K. The Cp(T) dependence of both compositions is characterized by the presence of two diffuse anomalies near the Burns temperature T-d and the temperature of the maximum in permittivity T-m in the temperature ranges 250-350 K and 120 200 K. The anomalous heat capacity near T-d was analysed taking into account the distribution of Zr concentration in nanoregions leading to the distribution of their transition temperatures into the polar phase. Excess heat capacity near Tm was discussed in the framework of the spherical random bond-random field model. The results are compared with the data obtained by the same procedures for PbMg1/3Nb2/3O3 studied experimentally earlier.
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15.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S., Melnikova S. V., Flerov I. N., Vasiliev A. D., Kruglik A. I., Kokov I. T.
Заглавие : Phase transitions in Cs2CdI4 single crystals
Место публикации : Phys. Status Solidi A. - 1988. - Vol. 105, Is. 2. - P.441-446. - ISSN 0031-8965
Ключевые слова (''Своб.индексиров.''): calorimetry--crystals - structure--dielectric properties--optical properties--x-ray analysis--birefringence--cesium cadmium iodide--dielectric permeability--specific heat--symmetry--cesium compounds
Аннотация: Cs//2CdI//4 crystals were grown from the melt (A) and from water solution (B). Optic, dielectric, X-ray, and calorimetric investigations were carried out. Crystal A shows three phase transitions at 332. 3, 259. 6, and 183. 4 K with the following sequence of phases: commensurate orthorhombic of beta -K//2SO//4 type ( alpha //0 equals 1. 074, b//0 equals 0. 8458, c equals 1. 4852 nm) B ARR LR incommensurate B ARR LR monoclinic ferroelastic (P2//1/n) B ARR LR triclinic ferroelastic (P1 OVER BAR ). The B-crystal belongs to monoclinic symmetry (P2//1/m) and undergoes transformation into the orthorhombic phase of beta -K//2SO//4 type at 420 K.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S., Blat D. H., Zinenko V. I., Iskornev I. M., Kruglik A. I., Flerov I. N.
Заглавие : Investigation of ferroelectric phase transitions in CsLiMoO//4 type crystals
Коллективы : European Meeting on Ferroelectricity
Место публикации : European Meeting on Ferroelectricity (5 ; 1983 ; Sept. ; 26-30 ; Malaga, Sp). Ferroelectrics. - 1983. - Vol. 54, Is. 1. - P.573-576. - ISSN 0015-0193
Ключевые слова (''Своб.индексиров.''): calorimetry--cesium compounds - x-ray analysis--phase transitions--ferroelectric materials
Аннотация: X-ray and calorimetric investigations of successive phase transitions (PTs) in crystals of CsLiMoO//4 type were made. The theoretical model description of these PTs as of order-disorder type ones is suggested and thermodynamical properties of the model are discussed.
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17.

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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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Kartashev A. V., Molokeev M. S., Isaenko L. I., Zhurkov S. A., Fokina V. D., Gorev M. V., Flerov I. N.
Заглавие : Heat capacity and structure of Rb2KMeO3F3 (Me: Mo, W) elpasolites
Коллективы : Siberian Branch of the Russian Academy of Sciences [34]; Russian Federation for the Support of Leading Scientific Schools of the Russian Federation [NSh-4645.2010.2]
Место публикации : Solid State Sci.: ELSEVIER SCIENCE BV, 2012. - Vol. 14, Is. 1. - P.166-170. - ISSN 1293-2558, DOI 10.1016/j.solidstatesciences.2011.11.019
Примечания : Cited References: 12. - This study was supported by the Siberian Branch of the Russian Academy of Sciences (Grant no. 34) and 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).
Предметные рубрики: T PHASE-DIAGRAM
Rb2KMoO3F3
TRANSITION
Ключевые слова (''Своб.индексиров.''): oxyfluorides--crystal structure--phase transition--calorimetry
Аннотация: X-ray and heat capacity measurements were performed on Rb2KMoO3F3 and Rb2KWO3F3 single crystals. A significant difference in the thermal parameters of atoms in 4a and 8c sites of Fm-3m structure was found, which depended on the central atom. Calorimetric measurements have revealed the heat capacity anomalies at 195 and 67 K, respectively, in Rb2KMoO3F3 and Rb2KWO3F3. The standard molar enthalpy and entropy were determined. Entropy changes associated with phase transitions in oxyfluorides under study and related Rb2KTiOF5 are discussed. 2011 Elsevier Masson SAS. All rights reserved.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mel'nikova S. V., Pogoreltsev E. I., Flerov I. N., Laptash N. M.
Заглавие : Unusual sequence of phase transitions in (NH4)3TiF7 detected by optic and calorimetric studies
Коллективы : Russian Foundation for Basic Research [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. 165. - P.14-19. - ISSN 0022-1139, DOI 10.1016/j.jfluchem.2014.05.016. - ISSN 1873-3328
Примечания : Cited References: 13. - This work was supported by Russian Foundation for Basic Research (Grant 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 no. NSh-924.2014.2).
Предметные рубрики: CRYSTAL-STRUCTURE
DIFFRACTION
NH4F
Ключевые слова (''Своб.индексиров.''): cubic fluorides--phase transitions--crystal-optic--calorimetry
Аннотация: For the first time structural transformations were observed for one of the compounds belonging to the family of double salt fluorides A3MeF7 = A2MeF6·AF. Single crystals of (NH4)3TiF7 = (NH4)2TiF6·NH4F were grown by evaporation of the aqueous solution. Polarizing optical observations, heat capacity and birefringence Δn = (no − ne) measurements were performed in a wide temperature range 100–400 K. Two reversible, first order structural phase transitions were found to be followed by an unusual sequence of symmetry changes: cubic (G3) (T2↓ = 287.5 K; T2↑ = 291–310 K) ↔ P4/mnc (G2) (T1↓ = 358.5 K; T1↑ = 360 K) ↔ 4/m (G1). The twin structures observed were described assuming the existence of cubic parent phase G0 with P m 3 ¯ m symmetry.
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Melnikova S. V., Shabanova L. A., Zaitsev A. I., Parshikov S. A., Ageev O. A., Aleksandrov K. S.
Заглавие : Ferroelastic phase transition in Cs3Bi2I9 crystal
Место публикации : Ferroelectrics, Letters Section. - 1996. - Vol. 20, Is. 5-6. - P.163-167. - ISSN 0731-5171
Ключевые слова (''Своб.индексиров.''): birefringence--cesium compounds--crystal symmetry--crystals--differential scanning calorimetry--elasticity--ferroelectricity--permittivity--stiffness--twinning--cesium bismuth iodide--elastic constant--elastic stiffness--ferroelastic phase transition--phase transitions
Аннотация: Phase transition (PT) was found in Cs3Bi2I9 single crystal at T0=223 K. Optical birefringence, dielectric and elastic constants and differential scanning calorimetry have been studied. It was found that birefringence ?nc and twinning picture appeared on (001) - and (100) - plates below T0, as well as softening of elastic stiffness C44 above T0. It allows to classify the PT as proper ferroelastic one with symmetry change 6/mmm - 2/m. В© 1996 OPA (Overseas Publishers Association) Amsterdam B.V. Published in The Netherlands under license by Gordon and Breach Science Publishers SA.
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