EFFECT OF HYDROSTATIC-PRESSURE ON FERROELECTRIC AND RELATED PHASE-TRANSITIONS

Effects of hydrostatic pressure on the ferroelectric and related structural transitions are briefly reviewed. The lowest-order effect of pressure is a linear change of the transition temperature. The sign of the pressure coefficient of the transition temperature of a structural phase transition provides information on the transition mechanism. We then discuss the appearance of pressure-induced phases with a nearly linear boundary, and non-linear effects of pressure-induced phenomena, such as pressure-induced ferroelectricity and/or new phase transitions whose phase boundaries are non-linear in the pressure-temperature phase space. Other important topics for pressure study are critical phenomena around various kinds of critical points which exist as isolated points in the pressure-temperature space. Brief descriptions are given for the vanishing of ordered phases and for phase transitions in the three-dimensional space of temperature-pressure-electric field or solid solution content.