Porous alumina ceramics having a sandwich panel structure which consists of a porous layer sandwiched in the two thin high-density layers were prepared by the solid casting method using an alumina slip added air foam. Mechanical properties of the porous alumina ceramics with porosity of 10 to 80% were measured. The average bending strengths showed the higher values, e.g., 100MPa at 40% porosity and 20MPa at 75% porosity, as compared with customary porous alumina ceramics. The bending strength decrease of the porous alumina ceramics with porosity was not so high as an empirical equation by Coble and Kingery. It was considered that the enhancement of bending strength resulted in the existence of high-density layers at surface of porous alumina ceramics.
