Analysis of the phase content and Zr:Ti fluctuation phenomena in PZT sol-gel films with a nominal composition near the morphotropic phase boundary

PZT thin films are commonly used for piezoelectric sensors and actuators. Some applications require a film thickness of a few micrometers, which can be achieved by using a sol-gel process with several coating and annealing steps. We prepared sol-gel derived Nd-doped and undoped PZT (53/47) films on metallic substrates by various thermal annealing treatments. During the pyrolysis and the annealing process, a Zr:Ti fluctuation along the cross-section of the sol-gel films takes place. By means of transmission electron microscopy (TEM), electron diffraction and energy dispersive X-ray spectroscopy (EDX), the local Zr:Ti ratio and phase content have been estimated indicating a decreasing tetragonal distortion, especially for layers close to the substrate. These results are related to the microstructure of the films, taking into account the tensions resulting from the difference in the thermal expansion of the metallic substrate to the ceramic film and the crystallite size.