Reaction Mechanisms in the Formation of PZT Solid Solutions

Abstract

The solid‐state reactions occurring in the system PbO‐TiO 2 ‐ZrO 2 were investigated using constant heating rates up to 1000°C. DTA, dilatometric length changes, and XRD analysis were used for characterization. PbO and TiO 2 reacted exothermally to form the product PbTiO 3 with a large volume expansion between 450° and 600°C. Formation of PbZrO 3 from PbO and ZrO 2 occurred endothermally with a large volume expansion between 700° and 800°C. The expansion was due to reaction topology, differential molar volumes of products and reactants, and the pellet microstructure. In the formation of PZT from ternary powder mixtures, PT formed between 450° and 600°C, followed by PZT formation at >700°C with no measurable amounts of PbZrO 3 formed as determined by XRD analysis. The analysis of the mechanisms indicates that the overall kinetics of homogeneous PZT solid‐solution formation are determined by either the ionic transport within the perovskite lattice or the phase‐boundary reactions leading to perovskite formation and not by the diffusion of Ti across PbO, which is relatively rapid.