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Published online by Cambridge University Press: 10 February 2011
Rare earth (Gd+3 and Ce+3) substitution on La+3 sites of the sol-gel prepared Pb0.85La0.15TiO3 films is studied using x-ray diffraction, atomic force microscopy, Raman scattering, and electrical characterization techniques. With increasing content of rare earths an increase in the lattice tetragonality was evidenced from x-ray data. Raman spectra obtained form Pb0.85La0.15-xCexTiO3 (x=0.0–0.07) and Pb0.85La0.15-xGdxTiO3 (x=0.0–0.15) films show features characteristics of PbTiO3 perovskite. Frequency variations of the lowest soft mode as a function of the composition x and temperature corraborate the increased tetragonality in these films. The ferroelectric transition temperature, dielectric constant, and coercive field was found to increase with Gd content. The phase transition temperature and polarization values increase up to 5 at.% Ce doping while they decrease above that composition due to the reduced domain wall mobility caused by Ce precipitation. A slight increase in the surface roughness was observed with increasing rare earth content in these films.