'Pseudo-proper' ferroelectric phase transitions in oxyfluoride K^sub 3^WO^sub 3^F^sub 3

Based on the structural data on the phases of cryolite (ordered perovskite) K^sub 3^WO^sub 3^F^sub 3^, we develop a statistical model, which allows to describe the sequence of phase transitions observed in this compound using a unified approach. According to the model, the crystal possesses two stru...

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Bibliographic Details
Published in:Phase transitions 2014-06, Vol.87 (6), p.592
Main Authors: Ivliev, MP, Misyul, SV, Molokeev, MS, Sakhnenko, VP
Format: Article
Language:English
Subjects:
Ferroelectrics
Phase transitions
Statistical mechanics
Online Access:Get full text
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Summary:Based on the structural data on the phases of cryolite (ordered perovskite) K^sub 3^WO^sub 3^F^sub 3^, we develop a statistical model, which allows to describe the sequence of phase transitions observed in this compound using a unified approach. According to the model, the crystal possesses two structural subsystems: the K cations located in the octahedral positions and the WO^sub 3^F^sub 3^ octahedra in positions alternating with K cations. In the symmetric (cubic) phase, each subsystem can be found in one of the eight states. At decreasing temperature, an orientational phase transition in the subsystem of octahedra occurs first, followed by a phase transition to the low-temperature phase, caused by the loss of stability with respect to the ordering in the K cation subsystem. We find that the electric polarization occurs as pseudoproper and discuss the mechanisms of formation of the phase states.
ISSN:0141-1594
1029-0338