Optical anisotropy near the relaxor-ferroelectric phase transition in lanthanum lead zirconate titanate.

We examine the optical activity, birefringence, and transparency of Lanthanum-doped, lead zirconate titanate (PLZT 7/65/35) bulk ceramic wafer sections over visible and near-IR spectra and on heating. Optical transitions are compared to both crystallographic (rhombohedral-cubic) and domain (relaxor-ferroelectric) transitions identified with x-ray diffraction, dielectric, and calorimetry measurements. Optical activity and birefringence are shown to be enhanced for disordered domains near room temperature, to attenuate above the relaxor-ferroelectric transition and to gradually decay above the Curie point regardless of the initial poling state. The results are interpreted in light of the change of crystallographic symmetry due to the local strains induced by ferroelectric architecture. The heterogeneous local strains more strongly influence the optical properties than the macro-scale structure of the polycrystalline PLZT ceramic. This mechanism is significant for understanding optical rotation and birefringence in polycrystalline systems. Finally, the specific rotation (up to 350°/mm) lies among the highest reported for crystalline materials. Along with strong poling contrast and comparatively small dispersion for the unpoled state, these properties are promising for electro-optics applications. [ABSTRACT FROM AUTHOR]