COMPOSITIONAL HETEROGENEITY AND THE ORIGINS OF THE MULTICELL CUBIC STATE IN SN-DOPED LEAD-ZIRCONATE-TITANATE CERAMICS

A systematic study of Sn-doped lead zirconate titanate ceramics has be en carried out as a function of Sn and Ti contents. Dielectric constan t and remanent polarization measurements have been performed and compa red to our recent transmission electron microscopy study. The dielectr ic maximum was found to be associated with a multicell cubic state, ra ther than a macroscopic transformation into an antiferroelectric state . In addition, a strong deviation from Curie-Weiss behavior was observ ed for temperatures several hundred degrees above the permittivity max imum. Evidence is presented that the dielectric maximum is associated with a metastable locking of the incommensuration, rather than a phase transformation. Under application of an electric field, the metastabi lity is seemingly overridden, and a tripling of the dielectric constan t is observed. The strong enhancement of the dielectric softening is b elieved to arise due to a modulation of the phase on the incommensurat e structure by the electric field.