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The dependence of the bulk photovoltaic effect (BPE) on illumination intensity and wavelength has been studied in (Pb0.97, La0.03)(Zr0.52, Ti0.48)1-0.03/4O3 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 O2) 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 O2 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.

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Tungsten oxide gels were prepared by a sol-gel process from a tungsten ethoxide/ethanol/water solution (sol). Tungstic hydrates were observed in high-viscosity sol by Raman spectroscopy. As the sol is reduced to the gel, Raman bands ascribed to amorphous tungsten oxide appeared. The result of the Raman measurement shows that the structure of the gel changes progressively during heat treatment and that the amorphous tungsten oxide becomes a crystalline solid at 410°C.

Samples of (Pb0.97, La0.03)(Zr0.52, Ti0.48)1-0.03/4O3 (PLZT) ceramics with and without an A-site deficient composition of 1 mol% in ABO3 perovskite structures have been prepared by sintering at 1200°C for 2 h to investigate the photovoltaic response upon UV illumination, as well as the ferroelectric and piezoelectric parameters such as the polarization-electric field (P–E) hysteresis curve, strain constant, and dielectric constant. Results confirmed that the A-site deficient composition generates a photovoltaic current twofold higher than that in the sample without the deficient composition. In the ferroelectric and piezoelectric parameters, no significant difference was measured between the two samples. These results indicate that the photostrictor response is mostly determined by the photovoltaic properties and that the overall response speed of photostriction can be markedly improved by enhanced photovoltaic current.