synthesis of α-Al_2O_3 platelets using sodium sulfate flux

摘要

When powder mixtures of {Al_2(SO_4), + Na_2SO_4}or {γ-Al_2O_3, [obtained by heating Al_2(SO_4)_3, at 900 deg. C for 3 h] + Na_2SO_4} were heated in an alumina crucible at l l00 deg.C for l h, α-Al_2O_3 platelets were formed. The powder mixture of {Al_2(SO_4)_3 + 2Na_2SO_4} yielded aggregations of platelets that were less than 5 μm in size. The size of the aggregations increased in proportion to the amount of Na_2SO_4, and aggregations of l20 μm were obtained using a mixture of {Al_2(SO_4)_3+, + 6Na_2SO_4}. The powder mixture of {γ-Al_2O_3 + 2Na_2SO_4} yielded hexagonal platelets having an average diameter of 3.7 4m 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 Na_2SO_4, and platelets having an average diameter of 5 μm were obtained using a mixture of {γ-Al_2O_4, + 6Na_2SO_4).