| 摘要 |
A process for producing alpha -alumina power constituted by alpha -alumina single crystal particles comprises calcining at least one of transition alumina and a transition alumina precursor, in a gas atmosphere containing (1) at least 5% of F, Cl, Br and/or I, (2) at least 1% HF, HBr and/or HI, or (3) a component prepared from at least 1%, based on the total gas atmosphere, of F gas, Br gas and/or I gas, and at least 0.1% of steam. The percentages are by volume and based on the total gas atmosphere. The alpha -alumina single crystal particles have high purity, homogeneity, a narrow primary particle size distribution and an octahedral or higher polyhedral shape. The powder can be obtained from alumina raw materials of a variety of different kinds in an industrially advantageous manner, and is suitable as a raw material for abrasives, sintered products, plasma spraying materials, fillers, single crystals, supports for catalysts, fluorescent substances, encapsulants, ceramic filters and spacers for liquid cells. |
