No. 20032 Deposited with http://cryst.instr.yamaguchi-u.ac.jp/20031

Abstract:

The crystal structure of K₂ZnI₄ is refined at 24 temperatures above and below the paraelectric-ferroelectric phase transition temperature by means of X-ray diffraction to reinvestigate the mechanism of the phase transition in more detail. The temperature of the translation of K(1) and K(2) along the b-axis and the rotational angle of the ZnI₄ tetrahedron about the axis nearly parallel to the a-axis is obtained by the structural analyses. It is concluded that the mechanism of this phase transition is not the order-disorder type but the displacive one. The temperature variation of the anisotropic temperature parameter U₂₂ of K(1), K(2), I(1) and I(2) is coincident with the theoretical prediction for the displacive type phase transition proposed by Fujii and Matsubara [prog. Theor. Phys. 78 (1987) 177].

Keywords: structural analysis, paraelectric-ferroelectric phase transition, X-ray diffraction, displacive type, K₂ZnI₄, Sr₂GeS₄-type structure

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DEPOSITED DATA

list file (text 33KB) for paraelectric Phase I (403K, displacive model) of K₂ZnI₄

list file (text 39KB) for ferroelectric Phase II (240K, partially disordered model) of K₂ZnI₄