Studies of phases, phase transitions and properties of some plzt ceramics

Abstract

Lanthanum-doped lead zirconate titanate (PLZT) ceramics of composition 8/65/35 and 9/65/35 have been studied by electrical, optical and thermal means. The results obtained have been used to elucidate the nature and extent of the phases occurring and the phase transitions between them. Phase α is obtained by thermally depoling a ceramic. It is converted into phase β by the application of electric fields or stress. On removal of the electric field, phase β is retained below a temperature TD while it reverts back to phase α if the temperature is above Tt. If phase β is heated, it transforms into α at Tt, but there is no reverse transformation on cooling. The transition at Tt can be sharp for chemically homogeneous material. Phase α is found to be non-birefringent, even in a single grain. It has linear dielectric and elastic properties. Phase β is birefringent, ferroelectric and ferroelastic. The properties of the two phases and the transitions between them can be used to explain the effects of electric field on ceramic properties, particularly electro-optic and controllable light-scattering effects.