(Pb0.9La0.1)TiO3 thin films were deposited onto indium tin oxide-coated glass and Pt/Ti/SiO2/Si substrates by spin coating. One set of the solutions was sonication-treated during the sol preparation, while the other remained untreated for comparison. The results were analyzed in terms of perovskite developments, dielectric constants and losses, polarization behavior, and optical properties. Perovskite formation temperatures became lower by application of the sonication process. Furthermore, dielectric/ ferroclectric and optical transmittance properties were improved substantially.