Decomposition and microstructural evolution of aluminum titanate

Abstract The isothermal decomposition of aluminum titanate single crystals with a size of tens of micrometers or more has been studied. The decomposition proceeds with the formation of nodule structure with corundum in the center and rutile surrounding it in the aluminum titanate single crystal matrix. During decomposition, the rutile formed by decomposition precipitates at the interface between the aluminum titanate and the rutile, and the alumina dissolves in the rutile. The alumina dissolved in the rutile precipitates as corundum at the rutile–corundum interface and replaces the rutile. This replacement precipitation then continues the decomposition reaction. Since there is no change in the solubility limit in the isothermal reaction, the decrease in thermodynamic energy due to the decomposition reaction is the driving force for the precipitation of corundum. An effective way to retard the decomposition reaction is to prevent the precipitation of corundum at the rutile interface. Before the decomposition reaction occurs, layers with many dislocations are formed on the particle surface, and it is suggested that the decomposition reaction initially occurs within this layer. The decomposition reaction proceeds in layers, and steps corresponding to these layers are formed on the rutile surface.