La content dependence of electrooptic properties of polycrystalline (Pb,La)(Zr_0.65,Ti_0.35)O₃ thick films

The systematic investigation of the electrical, optical and electrooptic properties of lanthanum-substituted lead zirconate titanate (PLZT) films was carried out. Polycrystalline PLZT films with various La and Pb contents were prepared at various sintering temperatures by chemical solution deposition (CSD). Among the 135 conditions we examined, a sintering temperature of 700 °C and a Pb content ratio of 125% relative to a stoichiometric value were optimum for preparing well-filled films. The maximum polarization monotonically decreased with increasing La content, while the dielectric constant change was maximum at a La content of 6 mol %. The refractive indexes of the PLZT films were estimated to be in the range from 2.35 to 2.42 at 630 nm. The refractive index change due to the application of a DC bias voltage was maximum at a La content of 0 mol%, monotonically decreased with increasing La content, and strongly correlated with the maximum polarization change. Therefore, we concluded that the electrooptic effect in the PLZT films is mainly caused by the reconfiguration of the domain structure in the films.