Pressure and temperature dependence of dielectric properties of lithium potassium sulphate

Abstract

The pressure (p) and temperature (T) dependence of the dielectric and dilatometric properties of single crystal LiKSO 4 have been measured in the pressure range up to 8 kbar and over the temperature range -120 to +70 degrees C. The stability range of the intermediate phase II decreases as the pressure rises and phase II disappears at a triple point. This phase is stable over the range -84<T<-63 degrees C on cooling and -79<T<-22 degrees C on heating at atmospheric pressure. The triple point also varies with heating/cooling, being at -59.0+or-0.5 degrees C, 2.1+or-0.1 kbar on cooling or increasing pressure and 16.5+or-0.3 degrees C. 4.3+or-0.1 kbar on heating or decreasing pressure. The variation of permittivity and spontaneous polarisation with temperature is explained in terms of the free energy and the piezoelectric coupling.