Normal-to-relaxor ferroelectric transformations in lanthanum-modified lead zinc niobate–lead zirconate titanate (PZN–PZT) ceramics

Dielectric permittivities of unpoled and poled lanthanum-modified lead zinc niobate-lead zirconate titanate (PZN-PZT) ceramics were investigated. Results showed that the relaxor characteristics were enhanced with an increase in La doping. Two characteristic temperatures Tnr (normal-to-relaxor transformation) and Trt (rhombohedral-to-tetragonal phase transition) were spontaneously observed in the poled specimens. Tnr and Trt both decreased with increasing La doping content. Temperature-dependent Sawyer-Tower polarization studies revealed a double hysteresis loop near Trt. The presence of the double hysteresis loop and the step in permittivity-temperature curves at Trt might imply a rhombohedral-to-tetragonal phase transition.