Synthesis of α-Al2O3 platelets using sodium sulfate flux

When powder mixtures of {Al-2(SO4)(3) + Na2SO4} or {gamma-Al2O3 [obtained by heating Al-2(SO4)(3) at 900 degrees C for 3 h] + Na2SO4} were heated in an alumina crucible at 1100 degrees C for 1 h, alpha-Al2O3 platelets were formed. The powder mixture of {Al-2(SO4)(3) + 2Na(2)SO(4)} yielded aggregations of platelets that were less than 5 mu m in size. The size of the aggregations increased in proportion to the amount of Na2SO4, and aggregations of 120 mu m were obtained using a mixture of {Al-2(SO4)(3) + 6Na(2)SO(4)}. The powder mixture of {gamma-Al2O3 + 2Na(2)SO(4)} yielded hexagonal platelets having an average diameter of 3.7 mu m and an average thickness of 0.3 mu m 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 mu m were obtained using a mixture of {gamma-Al2O3 + 6Na(2)SO(4)}.