Bulk photovoltaic effect in reduced/oxidized lead lanthanum titanate zirconate ceramics

The dependence of the bulk photovoltaic effect (BPE) on illumination intensity and wavelength has been studied in (Pb 0.97 , La 0.03 )(Zr 0.52 , Ti 0.48 ) 1-0.03/4 O 3 ceramics normally sintered at 1200° C for 2 h and then heat-treated in various atmospheres such as nitrogen, air and oxygen at 900° C for 1 h to investigate the enhancement of the BPE in the nitrogen-treated sample. The values of the Glass constant and the photoconductivity increased with decreasing oxygen partial pressure ( p O 2 ) during the heat treatments, whereas that of the dark conductivity decreased, indicating the creation of oxygen vacancies. No significant change was observed in ion oxidation states in the heat-treated samples by X-ray photoelectron spectroscopic analysis. The wavelength showing the maximum value of the photovoltaic current became shorter with decreasing p O 2 during the heat treatments and simultaneously the value of the maximum current notably increased. At the same time broadening of the current curves was also noted in the spectral responses. It is proposed that some of the electrons originating from the formation of oxygen vacancies can be expected to contribute to the enhancement of the BPE.