Perovskite-like fluorides and oxyfluorides: Phase transitions and caloric effects

Flerov, I. N.; Горев, М. В.; Tressaud, A.; Laptash, N. M.

doi:10.1134/s106377451101010x

Cited by 51 publications

(42 citation statements)

References 17 publications

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“…Of course the fall of δS 2 as well as δV 2 under pressure is not common peculiarity of phase transitions. For example, recent studies of the T -p phase diagrams in some perovskite-like ferroelastics have shown the constancy of the entropy jump at phase transition point at least in the range of p = 0 -0.5 GPa [25,26].…”

Section: Resultsmentioning

confidence: 99%

Thermal, dielectric and barocaloric properties of NH4HSO4 crystallized from an aqueous solution and the melt

Mikhaleva

Flerov

Карташев

et al. 2017

Solid State Sciences

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The study of heat capacity, thermal dilatation, permittivity, dielectric loops and susceptibility to hydrostatic pressure was carried out on the quasi-ceramic samples of 1 Direct measurements of pressure effect on permittivity and thermal properties showed dT 2 /dp = -123 K•GPa -1 which is consistent well in magnitude and sign with the baric coefficient evaluated using dilatometric and calorimetric data in the framework of the Clausius-Clapeyron equation. Thus, the temperature region of the ferroelectric Pc phase existence extends under pressure. Strong decrease in the entropy jump at the Pc ↔ P1 transformation with pressure increase as well as linear dependence of T 2 against pressure lead one to conclude that pressure shifts this phase transition towards the tricritical point on T -p phase diagram. Significant barocaloric effect was found in the region of the Pc ↔ P1 phase transition.

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Section: Resultsmentioning

confidence: 99%

Thermal, dielectric and barocaloric properties of NH4HSO4 crystallized from an aqueous solution and the melt

Mikhaleva

Flerov

Карташев

et al. 2017

Solid State Sciences

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“…В большей степени изучены фазовые переходы во фтори-дах и оксифторидах с октаэдрическими анионами [3][4][5]. С другой стороны, несомненный интерес в качестве цен-тральных атомов Me представляют металлы, которые в зависимости от валентности способны в совокупности с фторными и фторкислородными лигандами X образо-вывать полиэдры различной конфигурации.…”

Section: Introductionunclassified

Тепловые, оптические и диэлектрические свойства Rb-=SUB=-2-=/SUB=-TaF-=SUB=-7-=/SUB=-

Погорельцев¹,

Мельникова²,

Карташев³

et al. 2017

Физика Твердого Тела

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Выполнены исследования теплофизических, оптических и диэлектрических свойств Rb 2 TaF7. Изменение химического давления во фторидах A + 2 TaF7 за счет катионного замещения аммония рубидием не по-влияло на сегнетоэластическую природу структурных искажений, но привело к стабилизации высоко-и низкотемпературной фаз и к росту двулучепреломления. Энтропия фазового перехода P4/nmm ↔ Cmma характерна для превращений типа смещения, что согласуется с моделью структур исходной и искаженной фаз. Анизотропия химического давления является причиной изменения знаков аномальной деформации и барического коэффициента dT /d p для Rb 2 TaF7 по сравнению с наблюдаемыми для аммонийного аналога.Исследование выполнено при финансовой поддержке РФФИ и правительства Красноярского края в рамках научного проекта № 16-42-243001.

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“…17 Intriguingly, inversion symmetry lifting distortions are more scarce in the more ionic fluoroperovskites (ABF 3 ) than in oxides, 18 despite polar phases commonly appearing in fluorides belonging to the ABF 4 , ABF 5 , A 5 B 3 F 19 and A 3 B 5 F 15 families. 17,19,20 Two specific centrosymmetric transition metal (M) double perovskite fluorides (A 2 BM F 6 ) include those belonging to the cryolite and elpasolite crystal families ( Fig.…”

Section: 14-16mentioning

confidence: 99%

Ferroelectricity ind0double perovskite fluoroscandates

Charles

Rondinelli

2015

Phys. Rev. B

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Ferroelectricity in strain-free and strained double perovskite fluorides, Na3ScF6 and K2NaScF6, is investigated using first-principles density functional theory. Although the experimental room temperature crystal structures of these fluoroscandates are centrosymmetric, i.e., Na3ScF6 (P 21/n) and K2NaScF6 (F m3m), lattice dynamical calculations reveal that soft polar instabilities exist in each prototypical cubic phases and that the modes harden as the tolerance factor approaches unity. Thus, the double fluoroperovskites bear some similarities to ABO3 perovskite oxides; however, in contrast, these fluorides exhibit large acentric displacements of alkali metal cations (Na, K) rather than polar displacements of the transition metal cations. Biaxial strain investigations of the centrosymmetric and polar Na3ScF6 and K2NaScF6 phases reveal that the paraelectric structures are favored under compressive strain whereas polar structures with in-plane electric polarizations (∼ 5-18 µC cm −2 ) are realized at sufficiently large tensile strains. The electric polarization and stability of the polar structures for both chemistries are found to be further enhanced and stabilized by a coexisting single octahedral tilt system. Our results suggest that polar double perovskite fluorides may be realized by suppression of octahedral rotations about more than one Cartesian axis; structures exhibiting in-or out-of-phase octahedral rotations about the c-axis are more susceptible to polar symmetries.

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Perovskite-like fluorides and oxyfluorides: Phase transitions and caloric effects

Cited by 51 publications

References 17 publications

Thermal, dielectric and barocaloric properties of NH4HSO4 crystallized from an aqueous solution and the melt

Thermal, dielectric and barocaloric properties of NH4HSO4 crystallized from an aqueous solution and the melt

Тепловые, оптические и диэлектрические свойства Rb-=SUB=-2-=/SUB=-TaF-=SUB=-7-=/SUB=-

Ferroelectricity ind0double perovskite fluoroscandates

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