Sinter-crystallisation kinetics of a SiO2–Al2O3–CaO–MgO–SrO glass-ceramic glaze

Abstract

This paper examines the microstructural development and kinetics of the sintering and crystallisation processes of a SiO2–Al2O3–RO (R = Ca, Mg, Sr) glass-ceramic glaze. Crystallisation and sintering kinetics were studied by DTA and HSM, respectively, at different heating rates. The kinetic parameters of crystallisation were determined by the usual methods (Kissinger, Kissinger-Akahira-Sunose, Ozawa and Augis-Bennet methods), and the Johnson–Mehl–Avrami–Kolmogorov (JMAK) model, with an Avrami index of n = 3, characteristic of the surface crystallisation of very fine glass particles, was found to describe crystallisation kinetics very well. Sintering could also be described by the JMAK model, but with n < 1. Assuming the effect of temperature on the sintering rate to be the same as that of this variable on the inverse of glass matrix viscosity, a model was developed, based on the JMAK model, which only required a single fitting parameter. As the heating rate increased, the degree of overlap between the sintering and crystallisation processes was verified to decrease.