Low Temperature Dielectric Properties of (Rb_1-xK_x)₂ZnI₄ Mixed Crystals

Abstract

Rb₂ZnI₄ shows phase transitional anomalies at about 4 K and about 62 K in the temperature dependence of the dielectric constant. To investigate those, the mixed systems (Rb_1-xK_x)₂ZnI₄ and Rb₂Zn_1-xCd_xI₄ were prepared by both evaporation from the aqueous solution and Czochralski method from the melt. Dielectric constant, spontaneous polarization and thermal expansion measurements were performed for such mixed systems. For (Rb_1-xK_x)₂ZnI₄, the phase diagram was completed over full range of concentration x.

Keywords:

• Quantum ferroelectricity
• phase transition
• Rb₂ZnI₄
• K₂ZnI₄
• Rb₂CdI₄
• thermal expansion

Acknowledgments

We wish to express our thanks to Mr. R. Muraki for their assistance of the present experiments. We would like to thank Mr. S. Ikeda of Rigaku Corp. for the determination of the composition of our samples using a wavelength dispersive X-Ray fluorescence spectrometer (ZSX Primus).

Notes

Our previous study confirmed ferroelsectric activity in x = 0.13 sample [9].