Thermal Hysteresis Accompanying the Incommensurate-Commensurate Phase Transitions in Rb2ZnBr4 and Rb2ZnCl4

Atomic coordinate analysis allows materials with appropriate but previously unrecognized dielectric properties to be predicted as new ferroelectrics if their crystal structure is known. An earlier such prediction that NaSb3F10is ferroelectric is confirmed herein without ambiguity. Its spontaneous polarizationPsis found to exhibit reproducible dielectric hysteresis at room temperature, withPs≃ 60 µC m−2, under the application of a field of 0.3 MV m−1or greater. The pyroelectric coefficient 〈p〉 = 17 (5) µC m−2 K−1at 298 K. NaSb3F10undergoes a phase transition atTC≃ 461 K, on correction for thermal hysteresis, with entropy change ΔS= 5.7 (3) J mol−1 K−1. The colorless crystals melt atTm ≃ 515 K and decompose above ∼600 K. The thermal hysteresis of ∼35 K inTC, on heating and cooling at 5–25 K min−1, is typical of first-order phase transitions. The space group in ferroelectric phase III isP63, and that in phase II is predicted to beP6322, a nonpolar supergroup ofP63; the supergroup expected in the prototypic nonferroic phase I isP63/mmc. The space group of phase III isnota direct subgroup of phase I. The dielectric permittivity ∊′ at 1 kHz increases over an order of magnitude between 300 K and a major inflection atTC, continuing to increase steadily thereafter toTm.

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Effect of impurities on the incommensurate-commensurate phase transitions in Rb2ZnCl4, K2ZnCl4and Rb2ZnBr4

Ferroelectrics ◽

10.1080/00150198108218118 ◽

1981 ◽

Vol 36 (1) ◽

pp. 343-346 ◽

Cited By ~ 70

Author(s):

Katsumi Hamano ◽

Kenji Ema ◽

Shunsuke Hirotsu

Keyword(s):

Phase Transitions ◽

Commensurate Phase ◽

Effect Of Impurities

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Ultrasonic study of the normal — incommensurate — commensurate phase transitions in [N(CH3)4]2ZnCl 4

Journal de Physique ◽

10.1051/jphys:01986004703048300 ◽

1986 ◽

Vol 47 (3) ◽

pp. 483-489 ◽

Cited By ~ 27

Author(s):

J. Berger ◽

J.P. Benoit ◽

C.W. Garland ◽

P.W. Wallace

Keyword(s):

Phase Transitions ◽

Ultrasonic Study ◽

Commensurate Phase

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Irreversible Thermodynamic Discussions about Ferroelectric Phase Transitions

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.756-759.4419 ◽

2013 ◽

Vol 756-759 ◽

pp. 4419-4422

Author(s):

Jin Song Wang

Keyword(s):

Phase Transitions ◽

Ferroelectric Phase ◽

Thermal Hysteresis ◽

Intrinsic Property ◽

Irreversible Thermodynamic ◽

Irreversible Thermodynamics ◽

Minimum Entropy ◽

First Order ◽

Minimum Entropy Production ◽

Ferroelectric Phase Transitions

The irreversibility of ferroelectric phase transitions has been studied by using the irreversible thermodynamics. The thermal hysteresis of first-order ferroelectric phase transitions and the polydomain structure of ferroelectrics can be explained on the basis of the principle of minimum entropy production. A conclusion has been derived that the thermal hysteresis is not an intrinsic property of a system in which a first-order ferroelectric phase transition occurs. The finiteness of the systems surface is connected with the thermal hysteresis.

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