Formation and Evolution of Noncrystalline Phase in Reaction-sintering of ZrSiO_4/α-Al2O3 Mixed Powder

A noncrystalline phase can be formed in the reaction sintering of ZrSiO4/aaaaaaa-Al2O3 mixtures by solid reaction between ZrSiO4 and aaaaaaaaaa-Al2O3. The formation and evolution of the noncrystalline phase was investigated by using XRD and TEM techniques. It is shown that the noncrystalline phase formed at 1400℃, where mullite initially formed, is rich in Al2O3 in comparison with stoichiometric mullite, and, with the temperature increasing, it evolves to be rich in SiO2 due to the enhanced dissociation of ZrSiO4 and also the formation of Al2O3-rich mullite. The formation and evolution of the noncrystalline phase is closely related to the growth mechanisms of mullite.