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

Abstract

Sol–gel derived La modified lead zirconate titanate (PLZT) films were coated on glass substrates by the dip-coating method. The calcination temperature was varied between 490°C and 650°C for 1 h. Films with different thickness from 170 to 700 nm, in which the crystalline phase was randomly formed, were prepared. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to observe the morphology, thickness and phase status of the film, respectively. In conclusion, the thickness limits to the perovskite and pyrochlore phase formations are 150 and 230 nm, respectively. The pyrochlore phase can stabilize in thinner films with a film microstructure of the compositional fluctuation type and the perovskite phase stabilizes 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 perovskite 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.