Investigation of high-temperature reactions within the ZrSiO4–Al2O3 system

Solid state reactions between ZrSiO4 and αAl2O3 in powders of stoichiometric composition 3Al2O3·2SiO2 were studied by X-ray diffraction and electron scanning microscopy with energy dispersive X-ray analysis (SEM + EDX). Data were obtained at temperature ranging from 1400 °C to 1600 °C for a period of time ranging from 30 min to 60 h. The results indicate that ZrSiO4 and αAl2O3 react and form crystalline ZrO2, crystalline mullite (almost 3Al2O3·2SiO2 composition) and non-crystalline silicon–alumina phase (pre-mullite). At the temperature of 1600 °C the fastest stage of reaction is dissociation of ZrSiO4. Obtained results show that dissociation of zircon is a first-order reaction. The dissolution of Al2O3 particles and diffusion of Al into non-crystalline phase seem to be the slowest step of the reaction.