Non-steady-state photo-EMF in relaxor ferroelectrics: On the way to non-steady-state photo-thermo- and photo-thermopolarization-EMF

The non-steady-state photoelectromotive force is excited in PbNi1/3Nb2/3O3 and PbNi1/3Ta2/3O3 single crystals at corresponding light wavelengths λ=457, 532 nm. The experiments are carried out with the paraelectric phases of the crystals, i.e., above the temperature of phase transformation in the relaxor ferroelectric state. The photoelectric parameters, such as the type, value, and relaxation time of photoconductivity, as well as the diffusion length of carriers are estimated from the characteristics of the signal. There is a mismatch in behavior of the non-steady-state photoelectromotive force (photo-EMF) signal and photoconductivity response at high oscillation frequencies. The influence of nonuniform laser heating is proposed as the origin of this mismatch, and the ensuing theory of the non-steady-state photo-thermo- and photo-thermopolarization-EMF is developed.