PROCESS FOR THE PREPARATION OF SINTERED ALUMINA CERAMICS PARTICULARLY FOR USE IN MINERAL OIL MINING

According to the process of the present invention an aluminium compound - preferably aluminium hydroxide, bohmite, gamma-aluminium oxide or alpha-aluminium oxide or a mixture thereof - is activated with additives and sintered to yield ceramic shaped articles. The process of the present invention comprises adding to the aluminium compound(s) in an amount at least 0.05 % by weight - related to the aluminium oxide content thereof - yttrium oxide or lanthanun oxide or neodymian oxide or an equivalent amount of a salt thereof which can be converted into the corresponding oxide by heating: separately homogenizing the said mixtures by grinding and subjecting the same to thermal treatment at a temperature of at least 1450 C and thus reacting at least 80 % by weight of the said additives with aluminium oxide; thereafer admixing two or three of the activated aluminium oxides thus obtained and grinding the mixture thus obtained having a total additive content of 0.1-1.0 % by weight - expressed in pure oxides - and thereafter converting the ceramic basic materials thus obtained into shaped articles by known methods and finally sintering at a temperature above 1450 C.