Eur. Phys. J. B 5, 163-168 (1998)
https://doi.org/10.1007/s100510050430

Investigations on the soft-mode mechanism of the ferroelectric phase transition in K₂ZnI₄

Fachrichtung 10.2 Experimentalphysik, Universität des Saarlandes, 66041 Saarbrücken, Germany

Corresponding author: ^a mijoc@stud.uni-sb.de

Received: 7 April 1998
Revised: 5 June 1998
Accepted: 16 June 1998
Published online: 15 September 1998

Abstract

Dielectric and Raman spectroscopic measurements have been performed to investigate the ferroelectric phase transition in K₂ZnI₄. Single crystals were grown by the zone melting method. The frequency dependence of the dielectric permittivity from 1 MHz to 1 GHz has been studied in a temperature range between 265 and 285 K. A Debye like dielectric dispersion was found, showing a critical slowing down around K. Polarized Raman spectra have been taken between 220 and 310 K. Two softening modes have been found, one of A- and another one of B/B_g-symmetry. The phase transition mechanism in K₂ZnI₄ can be classified as partially order-disorder and partially displacive, confirming former structural results. It resembles strongly that of monoclinic K₂ZnI₄.