HUT36074A - Method for producing alumina ceramics of polycrystal structure - Google Patents

Abstract

Ceramic material with a polycrystalline structure contg. 92-99.9 wt.% alumina is prepd. by adding the 4-8 fold wt. of gamma-aluminum-oxide with a specific surface area of at least 5 square metre per g, and/or an equiv. aluminium cpd. to a mixt. of 15-35 mole% aluminium-oxide, 26-30 mole% lanthanum-oxide, 40-60 mole% niobium-oxide and/or the equiv. amts. of oxide forming salts provided one of the salts decomposes easily on heating, homogenising the mixt. by grinding, heating to 1250-1400 deg.C and grinding until 96 wt.% has a particle size of 1 micrometer. The resulting powder is mixed with the aluminium cpds. generally used in the ceramics industry to provide mixts. for ceramic prod. having a combined lanthanum-oxide and niobium-oxide content of 0.1-3.0 wt.%. - Opt. 1-5 wt.% other known additives can be mixed in. The resulting powder mixt. is ground until 70-90 wt.% has an particle size below 1 micrometer. After shaping in the known way the prods. are sintered at 1400-1600 deg.C.