Polarization kinetics of a photosensitive relaxor ferroelectric

Polarization switching in alternating quasi-static electric fields of frequency 10^?4 Hz and polarization relaxation in dc fields were studied in a photosensitive La-and Ce-doped barium-strontium niobate relaxor ferroelectric. Experimental data obtained in the thermal activation stage of the relaxation were used to reconstruct the relaxation time distribution spectrum. The characteristics of the polarization kinetics of an illuminated and a dark crystal are compared. It is shown that, in the crystal illuminated by light, the photoconductivity compensates for random electric and depolarization fields, thereby giving rise to a growth in amplitude of the dielectric hysteresis loops in the polarization versus field relation and to longer polarization relaxation times or increased heights of the potential barriers separating stable states from metastable states.