Structure evolution in the PbO-ZrO₂-TiO₂ sol-gel system: Part II—Pyrolysis of acid and base-catalyzed bulk and thin film gels

Abstract

The pyrolysis behavior of acid and base-catalyzed bulk and thin film Pb(Zr, Ti)O₃, or PZT, gels as well as their components have been studied using Thermo-Gravimetric Analysis (TGA), Differential Thermal Analysis (DTA), and Dynamic Mass Spectrometric Analysis (DMSA). The TGA/DTA data reflected the structural differences of the acid and base-catalyzed gels. Gels obtained using an acid catalyst were less cross-linked, denser, and more homogeneous than base-catalyzed gels. Based on the understanding of structure evolution in the silica system, the various events in the TGA/DTA studies of acid-catalyzed PZT gels were attributable to specific mechanisms. The DMSA showed that primarily water, 2-methoxyethanol, acetone, and carbon dioxide were evolved for both acid and base catalyzed PZT gels. The presence of the latter two volatiles was associated with the decomposition of the acetate group via the carbonate route. Acetate and carbonate groups were determined by Fourier Transform Intrared Spectroscopy (FTIR) to be present in the gel structure prior to pyrolysis. Differences in the synthesis of the prehydroiyzed solution were found to affect the amount of residual alkoxy groups, gel structure, pyrolysis behavior, and therefore, the resulting microstructures of sol-gel derived PZT thin films. Finally, some suggestions for improving the processing of sol-gel PZT thin films are given.