| 摘要 |
The present invention provides an alpha -alumina powder, which is suitable for use as a filler for silicone rubber or the like for manufacturing a heat-conductive sheet. The alpha -alumina powder includes alpha -alumina particles having an average particle diameter of not less than about 2 mu m and not more than about 5 mu m, a particle size distribution such that the ratio of 90 wt% diameter D90 to 10 wt% diameter D10 represented by D90/D10 is not more than about 2, and a crystalline form represented by an index A of more than about 0.40 and not more than about 0.50, wherein the index A is obtained by substituting X-ray intensities I(110), I(300) and I(116) at (110) plane, (300) plane and (116) plane, respectively, determined by X-ray diffraction, into the following formula (I): A = ä(110) + I(300)ü/ä2xI(116)ü |
