Ferroelectric phase transitions and three-dimensional phase diagrams of a Pb(Zr, Ti)O3 system under a hydrostatic pressure

Abstract

Effects of hydrostatic pressure on various ferroelectric phase transitions in Pb(Zr, Ti)O3 (PZT) have been investigated using the thermodynamic formalism based on the Landau–Devonshire phenomenological theory. For these purposes, the rotostrictive coefficient related to the coupling between the tilting of oxygen octahedron and the stress was evaluated first. We have then simulated three-dimensional phase diagrams of the PZT system using composition, stress and temperature as the three independent thermodynamic variables. It has been shown that, with increasing tensile hydrostatic pressure, the para–ferro transition temperature increases but the transition temperature between the two ferroelectric rhombohedral phases (FR(HT)–FR(LT)) decreases, and the morphotropic phase boundary moves slightly toward the tetragonal-phase field. Contrary to these, opposite tendencies are predicted under a compressive stress. The thermodynamic computation of ferroelectric properties in the vicinity of the FR(HT)–FR(LT) phase transition further suggests that a first-order phase transition gradually becomes a continuous second-order transition with increasing tensile stress.