LAUSR

Ceramics based on lead zirconate-titanate Pb(Zr0.70Ti0.30)O3 (PZT), bismuth manganite (BM) and the composite (1 − x) PZT–x BM were obtained. A systematic study of linear and nonlinear dielectric susceptibilities temperature and frequency dependences was conducted. A composition-induced crossover in nonlinear dielectric susceptibility was detected. The so-called scaled nonlinear susceptibility, a3, was obtained from experimental values of the real part of the linear and third-order nonlinear dielectric susceptibilities. The value for a3 was negative for low BM content in the whole temperature range specific to discontinuous ferroelectric phase transitions and relaxor behavior. In contradiction, a3 was positive for BM and for the composite with sufficiently high BM content. The positive a3 was attributed to a subsystem of dipoles created by trapped charges. Hopping charge transfer, which is a dominant mechanism for conduction in manganites, is responsible for the positive a3 and for the colossal magnitude of the imaginary part of the linear dielectric susceptibility. The concentration of the ions was determined using scanning electron microscopy. The chemical disorder and the precipitation of ions determined using time of flight–secondary ion mass spectrometry correspond to a crossover in the electrical features.