Quasi-ferroelectric state in Ba(Ti_1-xZr_x)O ₃ relaxor: Dielectric spectroscopy evidence

The dielectric spectroscopy of perovskite Ba(Ti_0.675Zr _0.325)O₃ (BTZ₃₂₅) relaxor ceramics is performed in a wide frequency range of 10^-2-10⁶Hz. In contrast to other known relaxors, where the dipole dynamics is subject to non-Arrhenius slowing-down and freezing upon cooling so that the cubic ergodic relaxor phase transforms into a cluster dipolar-glass phase or a ferroelectric phase, none of these transformations are observed in BTZ₃₂₅. In the course of cooling from the ergodic relaxor phase the characteristic time and the spectral width of the main relaxation process first increase rapidly in a Vogel-Fulcher manner, but then become almost temperature independent below the temperature of permittivity maximum, indicating the onset of the state which we call quasi-ferroelectric. The properties and the origin of this state are discussed.