Microstructural evolution of Pb(Zr, Ti)O₃ thin films prepared by hybrid metallo-organic decomposition

We report on the microstructural analyses of chemically prepared Pb(Zr_0.53Ti_0.47)O₃ (PZT 53/47) films. Although several techniques were used to analyze films, transmission electron microscopy (TEM) was emphasized. Phase evolution of these films, fabricated using hybrid metallo-organic decomposition (HMD), was determined by processing films at temperatures ranging from 500 °C to 650 °C. Our films, when observed with an optical microscope, appeared to consist of two distinct phases: (1) a featureless matrix and (2) 1–2 μm diameter “rosettes”. PZT films fired at 500 °C consisted of a pyrochlore containing phase (featureless matrix) and contained no perovskite, whereas films fired at 600 °C were ferroelectric and were approximately 90% perovskite (rosettes) by volume. Our TEM analysis showed that the pyrochlore-containing phase consisted of interpenetrating nanocrystalline pyrochlore and amorphous phases, both with dimensions on the order of 5 nm. For PZT films processed at 650 °C, the perovskite phase was observed in two forms: (1) large (≍2 μm) rosette structures containing 30 nm pores and (2) dense equiaxed particles on the order of 100 nm. We propose that phase evolution—with increasing temperature of HMD PZT 53/47 films—consists of the following steps: (1) phase separation, probably occurring in solution, (2) pyrochlore crystallization, (3) heterogeneous nucleation of perovskite PZT, and (4) homogeneous nucleation of perovskite PZT.