Influence of phase evolution and thermal decomposition kinetics on the properties of zircon ceramic.

In this study, the relationship between the decomposition process and properties of zircon ceramic was analysed. The decomposition process of zircon was investigated by kinetics model, thermodynamics and experimental phenomena. The Coats-Redfern and Kissinger models were used as basic kinetics models, and thermodynamics, thermogravimetry (TG) and differential scanning calorimetry (DSC) were used to characterize the decomposition process and calculate the kinetics parameters. The microstructure, pores characteristics, densification and physical properties were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Archimedes' principle. The results showed that the decomposition process of zircon could be divided into two stages, with the first and the second stages controlled by the phase boundary reaction and diffusion control reaction, respectively. The decomposition rate of the first decomposition stage was slow and the mechanism function was g(x) = 1-(1-α)1/3 while the decomposition rate of the second stage was fast and the mechanism function was g(x)=(1–2/3α)-(1-α)2/3. The large decomposition amount of zircon increased the amount of liquid phase, which would reduce the densification of zircon. [ABSTRACT FROM AUTHOR]