Aluminum nitride-based sintered body of high thermal conductivity

Claim 1

A process for preparing an aluminum nitride-based sintered body having a high thermal conductivity and a total oxygen content within the range of 0.01 to 20% by weight which comprises mixing powder ceramic components consisting essentially of as the main component, aluminum nitride powder containing 0.001 to 1% by weight of diffusible oxygen, with a rare earth element compound selected from the group consisting of oxides and carbonates of a rare earth element selected from the group consisting of Y, La, Pr, Nd, Sm, Dy and Gd, said rare earth element compound being capable of chemically fixing such diffusible oxygen, to supply 0.01 to 15% by weight of rare earth element based on the aluminum nitride-based sintered body, and sintering said powder mixture in an inert environment at a temperature of 1550° to 1950° C. and at a pressure and under conditions maintaining the total oxygen content within the above range to obtain said sintered body and to chemically fix said diffusible oxygen, the amount of total oxygen content in the sintered body being that due to said diffusible oxygen and that supplied in combination form with said rare earth element by said rare earth element compound.