| 摘要 |
The present invention provides an alpha-alumina powder, which is suitable for use as a filler for silicon 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 mum and not more than about 5 mum, a particle size distribution such that a 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): <paragraph lvl="0"><in-line-formula>A={I(110)+I(300)}/{2 xI(116)} (I) </in-line-formula>
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