Electro-optical properties and structures of (Pb, La)(Zr, Ti)O₃ and PbTiO₃ films prepared using aerosol deposition method

The electro-optical (EO) properties, film structures and far-infrared spectra were measured for lanthanum-modified lead zirconate titanate [PLZT, Pb_0.91La_0.09(Zr_0.65Ti_0.35)O ₃] and lead titanate [PT, PbTiO₃] films, prepared by the aerosol deposition (AD) method. The EO response appeared for AD films annealed at over 500°C, and increased as the annealing temperature increased. Downward shifts of the diffraction peaks, compared with diffraction peak positions of the corresponding to powders, were observed for as-deposited PLZT films in X-ray diffraction patterns of θ-2θ scans. The (200) peaks shifted to higher angles with increasing X-ray incidence angle to the film surface, indicating that the peak shifts were caused by lattice distortion induced by in-plane compressive stress. The (200) peaks shifted to the powder position when annealed at 600°C, which means that the annealing can relax the residual stress. Far-infrared spectroscopy measurements of reflectivity and transmittance were carried out on the PLZT and the PT powders and films, and the IR spectra of PT films were analyzed using the classical damped harmonic oscillator models to determine the oscillation parameters. We observed LO mode degradation and the broadening of the dielectric function peaks on the AD films. The frequencies of the E (1TO) soft-phonon mode of the annealed PT films were shown to have downward shifts of over 20cm^-1, compared with those of bulk ceramics and single crystals, suggesting that the AD may have induced a microscopic lattice degradation in the PT films, which may be responsible for the small EO response.