Features of phase transitions in lanthanum-modified lead zirconate titanate ferroelectric ceramics

摘要

The dielectric behavior and the ferroelectric properties (hysteresis loops) of Pb_(0.94)La_(0.06)(Zr_(0.80)Ti_(0.20))_(0.985)O_3 ferroelectric ceramics are analyzed considering the coexistence of the ferroelectric (FE) and the antiferroelectric (AFE) phases. The x-ray diffraction patterns and polarized light microscopy results reveal that FE and AFE ordering coexist. The dielectric analysis suggests two phase transitions. The first around 75 ℃, which is associatted to a ferroelectric (rhombohedral)-antiferroelectric (orthorhombic) phase transition; the second around 120 ℃, associated with an antiferroelectric (orthorhombic)-paraelectric (cubic) phase transition. The temperature dependence of hysteresis loops shows a double-loop-like behavior for temperatures above 75 ℃, showing a typical characteristic of an induced ferroelectric-antiferroelectric transformation.