| 摘要 |
Provided is a highly fillable low-soda α-alumina powder, which has a low soda fraction, an average particle diameter of 2 to 5 μm, a sharp particle size distribution, and a low viscosity during resin filling. Also provided is a production method therefor. The low-soda α-alumina powder, which is an α-alumina powder prepared from aluminum hydroxide obtained by the Bayer method, has excellent viscosity characteristics, a soda (Na2O) fraction of 0.1% by mass or less, an average particle diameter (Dp50) of 2 to 5 μm, a particle size distribution with an amount above 45 μm sieve (+45 μm) of 100 ppm or lower, and a span value [(Dp90 - Dp10)/Dp50] of 1.1 or lower. The α-alumina powder is prepared as follows: aluminum hydroxide having a soda (Na2O) fraction of 0.3% by mass or less is added with a halogen-type mineralization agent, fired so as to yield a formed density (forming pressure: 98.07 MPa) of 2.05 g/cm3 or greater and a BET specific surface area of 0.9 m2/g or less, and ground so that the particle size ratio (Dav/DBET), of the average particle diameter (Dav) after grinding over the BET-corresponding diameter (DBET) prior to grinding, is in the range of 1.10 to 1.45. |
