Microstructural observation was conducted to examine the effect of intentionally controlled inhomogeneity in starting mixtures on ZnAl2O4 formation in the presence of LiF and to clarify how the intermediate phase containing LiF, ZnO and Al2O3 affected the microstructure changes during the reaction. It was found that the formation of ZnAl2O4 with LiF was controlled by dissolution of reactants and precipitation of product accompanied by materials transport through the intermediate liquid phase.