Temperature-dependent reversible and irreversible processes in Nb-doped PbZrO₃relaxor ferroelectric thin films

The dielectric and ferroelectric nonlinearity of Nb-doped PbZrO3relaxor ferroelectric thin films was investigated. The ac field dependence of the permittivity of relaxor ferroelectric thin films is demonstrated to be described by a Rayleigh type relation. Both reversible and irreversible components of dielectric permittivity decrease linearly with the logarithm of the frequency of the ac field. The irreversible Rayleigh coefficient α'(T) shows a peak around the "freezing temperature" Tf, which is probably according to the transition from polar nano-regions (PNRs) to dipole-glass state in relaxor ferroelectrics. The results demonstrate that the models describing the interaction of domain walls and randomly distributed pinning centers in ferroelectric materials can be extended to the displacement of nanoscale walls in relaxors.