COEXISTENCE OF NORMAL AND DIFFUSE FERROELECTRIC-PARAELECTRIC PHASE-TRANSITIONS IN (PB,LA)TIO3 CERAMICS

Distinct evidence for the coexistence of a normal ferroelectric- paraelectric phase transition (NPT) at the Curie temperature and a diffuse phase transition (DPT) above the Curie temperature has been discovered in small-grained, nearly fully dense Pb1-xLa2x/3TiO3 (x=0.10) ceramics. It is found that the dielectric properties showed a strong dependence on the chemical composition of the materials and that these two types of phase transitions no longer coexisted in ceramics with x=0.05, with only a DPT around the Curie temperature. This observation of the coexistence of these two kinds of phase transitions may provide a clue to understanding the mechanism of DPTs which are observed in various ferroelectric materials. © 1990 The American Physical Society.