Limits of formation of random grown perovskite and pyrochlore phases in sol-gel derived La modified lead zirconate titanate thin films

Sol-gel derived La modified lead zirconate titanate (PLZT) films were coate d on glass substrates by the dip-coating method. The calcination temperatur e was varied between 490 degreesC and 650 degreesC for 1 h. Films with diff erent thickness from 170 to 700 nm, in which the crystalline phase was rand omly formed, were prepared. Scanning electron microscopy (SEM) and X-ray di ffraction (XRD) were used to observe the morphology, thickness and phase st atus of the him, respectively. In conclusion, the thickness limits to the p erovskite and pyrochlore phase formations are 150 and 230 nm, respectively. The pyrochlore phase can stabilize in thinner films with a film microstruc ture of the compositional fluctuation type and the perovskite phase stabili zes in thicker films with a film structure of the crystalline type cluster. The pyrochlore phase will start to transform into the perovskite phase as soon as the thickness is above the limit value for the formation of the per ovskite phase. The pure perovskite phase can be obtained by increasing the film thickness to 700 nm at most, instead of increasing the heat treatment temperature of the PLZT thin film. (C) 2000 Elsevier Science S.A. All right s reserved.