Abstract: Herein disclosed is alumina powder incorporated into a composition which should have excellent heat conduction and used as a heat-radiating member and for sealing a semiconductor. The spherical ?-alumina powder has an average sphericity of not less than 0.93 and a content of ?-crystalline form is not less than 95% and the spherical ?-alumina powder is prepared according to the method, which comprises the steps of: (1) softening metallic aluminum powder or alumina powder through the treatment with a flame; (2) solidifying the softened powder by passing the same through a zone maintained at a temperature ranging from 800 to 500° C.; (3) increasing the content of ?-phase by passing the solidified powder through a zone maintained at a temperature ranging from 950 to 1,500° C.; and (4) collecting the resulting powdery product while cooling the same.

Abstract: To provide an alumina powder having an improved flowability, a process for its production, and a resin composition employing it. An alumina powder which has an ?-phase content of at most 40% as measured by the following method, an average circularity of at least 0.

Abstract: Herein disclosed is alumina powder incorporated into a composition which should have excellent heat conduction and used as a heat-radiating member and for sealing a semiconductor. The spherical ?-alumina powder has an average sphericity of not less than 0.93 and a content of ?-crystalline form is not less than 95% and the spherical ?-alumina powder is prepared according to the method, which comprises the steps of: (1) softening metallic aluminum powder or alumina powder through the treatment with a flame; (2) solidifying the softened powder by passing the same through a zone maintained at a temperature ranging from 800 to 500° C.; (3) increasing the content of ?-phase by passing the solidified powder through a zone maintained at a temperature ranging from 950 to 1,500° C.; and (4) collecting the resulting powdery product while cooling the same.