Abstract
We predict a new non-steady-state optothermal electromotive force effect in relaxor ferroelectrics. The effect is observed and studied in a PbNi[Formula: see text]Ta[Formula: see text]O[Formula: see text] crystal at light wavelength [Formula: see text] nm and room temperature, which is significantly above the broad, frequency-dependent maximum of the permittivity ([Formula: see text] K), below which remanent polarization and the relaxor ferroelectric state arise. We focus on the pronounced mismatch in high-frequency behaviour of the non-steady-state EMF and conductivity response due to nonuniform laser heating and develop the ensuing theory of the effect.