Pyrochlore-to-perovskite transformation during rapid heating of sol-gel (Pb,La)TiO3 thin films

Phases appearing in lanthanum-modified lead titanate thin films prepared by a diol-based sol-gel method and crystallized by rapid heating were studied. The results clearly indicate that a phase transformation from a pyrochlore structure to the perovskite phase occurs in Pb-deficient films during the thermal treatment, which involves a heating rate higher than 500 degrees C min(-1). The rate of this transformation is a function of the lead content of the films, decreasing as lead volatilizes. Temperatures higher than 650 degrees C or soak times longer than 2 h make possible the complete pyrochlore-to-perovskite transformation without any lead excess in the films.