Synthesis of α-alumina platelets using flux method in 2.45 GHz microwave field

In the presence of sodium sulfate as a flux, α-alumina particles, composed of highly aggregated platelets, were synthesized by conventional thermal and microwave heating of Al2(SO4)3 powders at 900–1100 °C for 1 h in an alumina crucible. The size of α-alumina platelets increased with increasing flux concentrations and temperatures in both conditions of conventional thermal and microwave heating. However, the sizes and size distributions of α-alumina platelets obtained by microwave heating were smaller and narrower, relatively, compared to those obtained by conventional thermal heating. It was assumed that microwaves had a significant non-thermal effect in the stage of nucleation and crystal growth of α-alumina.