Pb(Zr0.52Ti0.48)O3(PZT) thin films were synthesized on a sapphire substrate for application as planar optical waveguide devices using a metalorganic decomposition (MOD) process. Pyrochlore phase, which always forms preferentially when the PZT thin films (~200 nm) are deposited on
a sapphire substrate directly, has been effectively suppressed by using a SrTiO3(STO)film (~190 nm) as a buffer layer. The PZT/sapphire thin films have a significantly larger refractive index than the STO/sapphire ones: n PZT=2.2012 and n STO=2.0639 (at 632.8 nm) by prism coupling measurement and n P'ZT=2.215 and n S'TO=2.084 (at 632.8 nm) by optical transmission spectroscopic measurement. The STO layer cannot only serve as buffer layer for enhancing the crystallization kinetics of the subsequently deposited PZT thin films, but can also serve as cladding layer in a ridge-type planar waveguide, which uses PZT thin film as core materials.