Abstract: The invention relates to a densely sintered tabular ceramic part of aluminum oxide having improved thermal shock resistance, which possesses a fine porosity of at most 10% by volume, does not contain inclusions having a diameter of .gtoreq.70 .mu.m within the ceramic microstructure and is not destroyed on immersion in a molten metal bath having a temperature of at least 350.degree. C. The invention also relates to a process for producing such a shaped part.

Abstract: The invention relates to a densely sintered tabular ceramic part of aluminum oxide having improved thermal shock resistance, which possesses a fine porosity of at most 10% by volume, does not contain inclusions having a diameter of .gtoreq.70 .mu.m within the ceramic microstructure and is not destroyed on immersion in a molten metal bath having a temperature of at least 350.degree. C. The invention also relates to a process for producing such a shaped part.

Abstract: Ceramic moldings composed of aluminum oxide which have a proportion of intercrystalline fracture of more than 50%, an average pore radius of more than 4 .mu.m and a porosity of more than 2%, are obtained by:a) grinding aluminum oxide which is at least 99.5% pure and has an average primary crystal size of 1 to 4 .mu.m to an average fragment size of 2 to 7 .mu.m,b) adding a source of magnesium oxide, silicon oxide and calcium oxide in amounts such that the magnesium oxide content is 0.2 to 2.5%, the silicon dioxide content is 1 to 6% and the calcium oxide content is 0.1 to 2.5%, in each case with respect to the amount of Al.sub.2 O.sub.3,c) shaping a green compact andd) sintering.