PEROVSKITE PHASE-FORMATION IN SOL-GEL DERIVED PB(ZRXTI1-X)O-3 THIN-FILMS

Thin films of lead zirconate titanate having the composition Pb-1.05(Z r0.53Ti0.47)O-3 were deposited by a sol-gel method on a set of crystal line and amorphous substrates. The thickness of the him was varied by controlling the sol concentration or by repeated coatings. Factors con trolling phase formation in the films such as nature of the substrate material, film thickness, chemical composition of the film, hearing ra te and gaseous atmosphere during the heat treatment were studied. On g lass substrates the pyrochlore phase was obtained in thin (0.4 mu m) f ilms and the perovskite phase in thicker (>1.5 mu m) films. Crystallin e substrates (except Si and stainless steel) yielded a perovskite phas e in 0.6 mu m thick film. Low Zr/Ti ratio, rapid heating and introduct ion of nitrogen in the later stage of heat treatment also favoured the formation of the perovskite phase. It is shown that Pb deficiency in the film caused by diffusion of Pb into amorphous substrates or by oth er mechanisms is primarily responsible for inhibiting the pyrochlore t o perovskite transformation. The initial crystallisation of the amorph ous film into pyrochlore rather than a perovskite phase (as in powders ) is proposed to be due to higher strain energy barrier which exists f or the amorphous to perovskite transformation in the film.