COMPOSITE OXIDE PARTICLE

PURPOSE:To obtain composite oxide particles useful as a filler for a composite resin required to transmit light rays such as a sealing material for optical semiconductor, a dental composite resin, etc., capable of reducing content of titania in comparison with a compound oxide of anatase type structure. CONSTITUTION:Composite oxide particles are spherical particles comprising silica and titania as main constituent components, having 0.05-50mum average particle diameter wherein the ratio of rutile type crystal titania in the whole titania is >=5mol%. A concentration of a silicon alkoxide compound and a titanium alkoxide compound is hydrolyzed to give a cohydrolyzate composed of silicon and titanium as main constituent, which is heated in a nonoxidizing atmosphere such as nitrogen or argon at 900-1,300 deg.C.