Effect of Hydrostatic Pressure on the Phase Transitions in (Rochelle Salt)_1−x(Ammonium Rochelle Salt)_x Mixed Crystal System

Abstract

The composition-pressure-temperature three dimensional phase diagram was determined for the system of (Rochelle salt)_1−x(ammonium Rochelle salt)_x from dielectric measurements in a range of 0≤x≤0.32, p\lesssim8 kbar, and −110°C\lesssimT\lesssim50°C. Both the upper and lower Curie temperatures increase with increasing hydrostatic pressure for x≤0.025, and the temperature range of the ferroelectric phase widens. In the composition range of 0.025<x≤0.039, the ferroelectric phase was observed as a pressure-induced phase. For the compositions of x=0.054 and 0.11, the ferroelectric phase was not found up to 8 kbar. Hydrostatic pressure depresses the Curie temperature of the low-temperature ferroelectric phase which is found in x\gtrsim0.18 with a large depression rate.