PURPOSE: To uniformize the size and distribution of closed pores and to enhance strength by heating and sintering a molded body of a mixture contg. prescribed amts. of fine powdery magnesium of a regulated particle diameter, org. beads of a regulated diameter and an org. binder under prescribed conditions.
CONSTITUTION: Fine powdery magnesium of 1-20μm average particle diameter is mixed with 1-20vol.% org. beads of 3-50μm diameter such as styrene polymer beads and an org. binder such as PVA. A molded body of the resulting mixture is heated to 350°C at ≤50°C/hr heating rate in the case of 1-10vol.% org. beads or at ≤20°C/hr heating rate in the case of 10-20vol.% org. beads. It is further heated to the sintering temp. at ≤200°C/hr heating rate and sintered at 1,550-1,700°C to obtain a porous magnesia sintered body having closed pores of 1-50μm pore diameter.