Synthesis of α–Al2O3 platelets using sodium sulfate flux

Abstract

When powder mixtures of {Al2(SO4)3 + Na2SO4}or {γ–Al2O3 [obtained by heating Al2(SO4)3 at 900 °C for 3 h] + Na2SO4} were heated in an alumina crucible at 1100 °C for 1 h, α–Al2O3 platelets were formed. The powder mixture of {Al2(SO4)3 + 2Na2SO4} yielded aggregations of platelets that were less than 5 μm in size. The size of the aggregations increased in proportion to the amount of Na2SO4, and aggregations of 120 μm were obtained using a mixture of {Al2(SO4)3 + 6Na2SO4}. The powder mixture of {γ–Al2O3 + 2Na2SO4 yielded hexagonal platelets having an average diameter of 3.7 μm and an average thickness of 0.3 μm. In addition to aggregation size, the size of the hexagonal platelets also increased in proportion to the amount of Na2SO4, and platelets having an average diameter of 5 μm were obtained using a mixture of {γ–Al2O3 + 6Na2SO4}.