| 摘要 |
PURPOSE:To efficiently prepare a light pervious alumina raw material powder by freely grinding high purity alpha-alumina having a special specific surface area or an alumina powder consisting of alpha-alumina and intermediate alumina and subsequently grinding the same in a closed system. CONSTITUTION:alpha-alumina obtained by the hydrolysis of an organoaluminum compound and having a mean particle size of 2mum or more, purity of 99.9% or more and a specific surface area of 1-70m<2>/g or an alumina powder consisting of alpha-alumina and intermediate alumina is freely ground by a jet mill and subsequently ground in a closed system by a vibration mill or a ball mill so that coarse particles of 1mum or more become below 10%. As a result, the grinding time due to a closed grinding medium is shortened and the generation amount of flocculated particles accompanied by the generation of minute particles is suppressed to make it possible to obtain alumina containing coarse particles of 1mum or more in an amount of 10% or less. An alumina sintered body using this alumina can be used in the light emitting tube of a high pressure sodium lamp, a high temp. window or a memory erasing window as high light pervious alumina. |
