Heat capacity, p-T phase diagram, and structure of Rb2KTiOF5

Fokina, V. D.; Flerov, I. N.; Мolokeev, Maxim S.; Pogorel’tsev, E. I.; Bogdanov, E. V.; Крылов, А. С.; Bovina, A. F.; Voronov, V. N.; Laptash, N. M.

doi:10.1134/s1063783408110280

Cited by 20 publications

(24 citation statements)

References 13 publications

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“…The large width (25 cm –1 ) of the line at 900 cm –1 in the distorted low temperature phase indicates that the octahedral ions remain partly disordered. This is in agreement with the model of distorted phase structure proposed by Fokina et al . The width of this line may be attributed to phonon anharmonicity and lattice disorder, but such a large value and its weak temperature dependence indicate that disorder is the main factor, and it remains intact under further cooling.…”

Section: Resultssupporting

confidence: 92%

“…We found considerable (about 6 K) hysteresis of line shifts at the transition point. This is in good agreement with available calorimetry data . According to quantum‐chemical calculations, the region near 900 cm –1 corresponds to nondegenerated ν 1 (TiO) vibration of free TiOF 5 3– ion.…”

Section: Resultssupporting

confidence: 88%

“…The microcrystalline powder of Rb 2 KTiOF 5 was synthesized by a solid phase reaction. The samples were taken from the same crystallization as described by Fokina et al …”

Section: Experimental Methods and Data Processingmentioning

confidence: 99%

“…Effects of hydrostatic pressure on transition temperature in Rb 2 KTiOF 5 have been studied previously only up to 0.6 GPa . It was shown that an increase in hydrostatic pressure increases temperature of transition from cubic phase and expands stability range of the tetragonal phase.…”

Section: Introductionmentioning

confidence: 99%

“…The studies of phase transitions in Rb 2 KTiOF 5 under cooling have shown the transition at T = 215 K from phase G 0 ( Fm 3 m ) into phase G 1 (probably I /4 m ), which was largely because of TiOF 5 octahedra ordering. Calorimetric studies have shown that this transition is accompanied by considerable entropy changes (∆ S ≈ R ln 8), typical for the order–disorder transformations. Temperature phase transitions were also observed in a similar structure (NH 4 ) 3 TiOF 5 .…”

Section: Introductionmentioning

confidence: 99%

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Raman scattering study of temperature and hydrostatic pressure phase transitions in Rb₂KTiOF₅ crystal

Крылов

Goryaĭnov

Vtyurin

et al. 2011

J Raman Spectroscopy

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Raman spectra of Rb2KTiOF5 crystal were obtained and analyzed in the temperature range from 77 to 297 K and under hydrostatic pressure up to 4.2 GPa (at T = 295 K). The experimental results were compared with quantum‐chemical simulation of TiOF5 pseudo‐octahedron. To interpret effects of lattice ordering, phonon spectra of several ordered phases of Rb2KTiOF5 were calculated within ab initio generalized Gordon–Kim model, and ordering of TiOF5 molecular groups were simulated within Monte Carlo approach. The spectra exhibited orientation disordering in the cubic phase under ambient conditions. Cooling below the phase transition temperature (215 K) leads to partial ordering of the structure. The isotropic perovskite‐like phase was found to undergo first‐order transition into a low‐symmetry anisotropic phase at about 1 GPa. Further compression up to 4.1 GPa did not show any effects associated with phase transitions. Copyright © 2011 John Wiley & Sons, Ltd.

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Section: Resultssupporting

confidence: 92%

Section: Resultssupporting

confidence: 88%

“…The microcrystalline powder of Rb 2 KTiOF 5 was synthesized by a solid phase reaction. The samples were taken from the same crystallization as described by Fokina et al …”

Section: Experimental Methods and Data Processingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Raman scattering study of temperature and hydrostatic pressure phase transitions in Rb₂KTiOF₅ crystal

Крылов

Goryaĭnov

Vtyurin

et al. 2011

J Raman Spectroscopy

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Room‐Temperature Colossal Elastocaloric Effects in Three‐Dimensional Graphene Architectures: An Atomistic Study

Zhao

Guo

Zhang

2022

Adv Funct Materials

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Solid‐state cooling exploits the thermal response of caloric materials when subjected to external physical fields and represents a promising alternative to conventional refrigeration technologies. However, existing caloric materials are often limited by relatively small caloric response and hysteresis issues rooted in first‐order structural transitions. Here, colossal and reversible elastocaloric effects near room temperature in superelastic graphene architectures are predicted by thermodynamic analysis and atomistic calculations. The estimated adiabatic temperature change can reach a value of 155 K under a compressive stress of 0.7 GPa in a wide temperature range of around 300 K, yielding outstanding elastocaloric strength and efficiency. More unique is that both cooling and warming can be realized in the materials by applying tensile and compressive strains to host conventional and inverse elastocaloric effects, respectively, with almost no fatigue behavior and hysteresis effect. Such unprecedented elastocaloric performance results from a strain‐induced large change in configurational entropy in the graphene architectures. These effects are potentially extendable to other superelastic nanomaterials and hence suggest new material settings for developing high‐performance solid‐state refrigerants.

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Calorimetric, dilatometric and DTA under pressure studies of the phase transitions in elpasolite (NH4)2KZrF7

Горев

Карташев

Богданов

et al. 2020

Journal of Fluorine Chemistry

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Heat capacity, thermal expansion, and sensitivity to the hydrostatic pressure of (NH 4 ) 2 KZrF 7 elpasolite are studied in a wide temperature range. The changes in deformation and entropy during successive phase transitions are determined: ∆(∆V /V ) = 3•10 −4 ; ∆S = 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 F m3m. 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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Heat capacity, p-T phase diagram, and structure of Rb2KTiOF5

Cited by 20 publications

References 13 publications

Raman scattering study of temperature and hydrostatic pressure phase transitions in Rb₂KTiOF₅ crystal

Raman scattering study of temperature and hydrostatic pressure phase transitions in Rb₂KTiOF₅ crystal

Room‐Temperature Colossal Elastocaloric Effects in Three‐Dimensional Graphene Architectures: An Atomistic Study

Calorimetric, dilatometric and DTA under pressure studies of the phase transitions in elpasolite (NH4)2KZrF7

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Heat capacity, p-T phase diagram, and structure of Rb2KTiOF5

Cited by 20 publications

References 13 publications

Raman scattering study of temperature and hydrostatic pressure phase transitions in Rb2KTiOF5 crystal

Raman scattering study of temperature and hydrostatic pressure phase transitions in Rb2KTiOF5 crystal

Room‐Temperature Colossal Elastocaloric Effects in Three‐Dimensional Graphene Architectures: An Atomistic Study

Calorimetric, dilatometric and DTA under pressure studies of the phase transitions in elpasolite (NH4)2KZrF7

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Raman scattering study of temperature and hydrostatic pressure phase transitions in Rb₂KTiOF₅ crystal

Raman scattering study of temperature and hydrostatic pressure phase transitions in Rb₂KTiOF₅ crystal