Effect of multiple impurity doping on the photovoltaic properties of lead zirconate-titanate ceramics

Pb(Zr-0.5, Ti-0.5)O-3 (PZT) ceramics singly doped with 0-3 mol% of Ta and t hose multiply doped with 1 mol% of Na and 0-4 mol% of Ta have been sintered at 1050-1300 degrees C for 2h to investigate the change in photovoltaic pr operties with changes in the concentration of Pb vacancies, and also grain size, upon ultraviolet irradiation. Both photovoltaic current and photovolt age were markedly increased by the doping of Ta in the case of single dopin g, whereas in the multiply doped samples they showed no significant change up to 1 mol% of doped Ta. Beyond this amount, however, they were found to s ignificantly increase. The average grain size in the singly doped samples d ecreased with increasing amounts of doped Ta, while that in the multiply do ped samples revealed a maximum at around 1 mol% Ta, below which grain size was smaller than that of the nondoped sample. It is concluded from these re sults that the formation of Pb vacancies onto the perovskite lattice, rathe r than the existence of doped Ta, has a fundamental significance on the pho tovoltaic properties in PZT ceramics.