F-center mechanism of long-term relaxation in lead zirconate-titanate-based piezoelectric ceramics. 1. After-heating relaxation

Abstract

Results of experimental investigation of relaxation aging processes in Pb(Zr,Ti)O3-based solid solutions after termination of external actions are presented. Heating, DC electric field, uniaxial pressure and some of their combinations were taken as external actions. In the main part of the present paper, we use heating as external action. The said processes are long-time one and are described by the logarithmic function of time.Reversible and nonreversible relaxation processes take place depending on the action intensity. The relaxation rate depends on the action intensity also, and the said dependence has nonlinear and nonmonotonic form if external action leads to domain disordering.The oxygen vacancies-based model for description of the long-time relaxation processes is suggested. The model takes into account oxygen vacancies on the sample’s surface ends, their conversion into [Formula: see text]- and [Formula: see text]-centers under external effects (due to the liberation of the pyroelectric charge) and subsequent relaxation of these centers into the simple oxygen vacancies after the actions termination. The initial sample’s state is electroneutrality one. F-center formation leads to the violation of the original sample’s electroneutrality, and generates DC electric field into the sample. Relaxation of F-centers is accompanied by decreasing of electric field, induced by them, and dielectric constant relaxation as consequent effect.