Influence of Illumination on Domain Switching and Photovoltaic Current in Poled (Pb 1-x La x )TiO₃ Ferroelectric Ceramics

The influence of photoexcited nonequilibrium carriers on domain switching and photovoltaic current was investigated in two kinds of poled La-modified PbTiO₃ ferroelectric ceramics, (Pb 0.85 La 0.15 )TiO₃ and (Pb 0.76 La 0.24 )TiO₃, under illumination in the absence of external electric field. Both photovoltaic current and cumulative AE event counts increased with illumination time. The observed nonsteady-state photovoltaic current could be explained on the basis of the cycles of a series of physical events consisting the establishment of space charge field by photoexcited carriers trapped at the grain boundaries, the photoinduced domain switching, and the increase in the remanent polarization. An analysis of energy distribution of the observed AE signals also revealed that the space charge field in (Pb 0.85 La 0.15 )TiO₃ allowed both 180˚ and 90˚ domains to be switched during illumination.