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

The dielectric behavior and the ferroelectric properties (hysteresis loops) of Pb0.94La0.06(Zr0.80Ti0.20)0.985O3 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 ∘C, which is associatted to a ferroelectric (rhombohedral)–antiferroelectric (orthorhombic) phase transition; the second around 120 ∘C, 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 ∘C, showing a typical characteristic of an induced ferroelectric-antiferroelectric transformation.