Polarization and depolarization behavior of hot pressed lead lanthanum zirconate titanate ceramics

Abstract

Studies have been made of the polarization and depolarization behavior for lead lanthanum zirconate titanate ceramics with zirconia: titania ratio 0.65/0. 35 and La₂O₃ content from 0.07 to 0.095 (7:65:35 to 9. 5:65:35). Continuity of the dielectric dispersion on cooling unbiased freshly de-aged samples suggests that across this whole composition range for temperatures below the dielectric maxima, there are no macroscopic phase changes. Large remanent polarizations may be built up at low temperatures by cooling under suitable DC bias, but the ceramics will 'stand off significant bias levels applied at low temperature and remain dispersive. Depoling on heating becomes progressively less abrupt with increasing La₂O₃ content but is always accomplished well below the temperature of the dielectric maximum. A model involving the ordering and disordering of polar micro-regions under electrical and thermal fields accounts vell for the observed properties.