Effect of lanthanum substitution on the Raman spectra of barium titanate thin films

Thin films of Ba1-xLaxTiO3 on platinum substrates were synthesized using the sol-gel method for x values of 0.0, 0.03, 0.05, and 0.10, and the effect of trivalent La3+ substitution on the structural and dielectric properties was studied. Using X-ray diffraction, structural analysis of these compositions revealed a slight increase in the tetragonal distortion of the unit cell with increase in La content. Accordingly, an increase in the tetragonal to cubic transition temperature T-T/C was detected by temperature-dependent Raman spectroscopy in the range of 70-500 K. Unlike the results from Raman scattering for the La-doped BaTiO3 films, the dielectric measurements showed broad and diffused dielectric maxima, making the estimation of the transition temperature merely qualitative. Copyright (C) 2006 John Wiley & Sons, Ltd.