The electrical conductivity behaviour in the paraelectric state has been investigated in lanthanum modified lead zirconate titanate (PLZT) ceramics, considering the universal relaxation law. The contribution of conductive processes to the dielectric response for the low-frequency range was discussed taking into account the oxygen vacancies mechanism. The activation energies for the thermally hopping and conductivity processes were obtained. The results for the frequency dependence of the conductivity suggest at the oxygen vacancy hopping processes, due to relaxations in oxygen vacancy-related dipoles, being mainly responsible for the conduction behaviour in the studied system.

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In this paper, the contribution of the domain walls motion to the dielectric and piezoelectric responses for the 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 system is investigated. A monotonically increasing temperature dependence of the dielectric permittivity is observed from very low temperatures up to the ferroelectric–paraelectric phase transition temperature. It is verified that the major contribution to dielectric response at room temperature is from the extrinsic effect. A linear dependence of the permittivity with the amplitude of the ac applied electric field is verified from the nonlinear dielectric measurement. Rayleigh's model is used to quantitatively evaluate the dielectric response, leading to similar behaviour of the typical soft PZT. On the other hand, direct piezoelectric response also displays a Rayleigh-type behaviour. Piezoelectric measurements show in the entire investigated dynamic stress range a decrease in the piezoelectric response with both increase in frequency of the applied dynamic stress and increase in the pre-stress on the samples.