Rare earth fluoride additive for sintering aluminum nitride

Claim 1

A process for producing a sintered polycrystalline aluminum nitride body having a porosity of less than about 10% by volume and a thermal conductivity of at least 0.5 W/cm·K at 25° C. which consists essentially of forming a mixture consisting essentially of aluminum nitride powder containing oxygen ranging in amount from greater than about 1.0% by weight to less than about 4.0% by weight and YF 3 , said YF 3 ranging from about 0.5% by weight to about 15% by weight based on the amount of said aluminum nitride powder, shaping said mixture into a compact, the aluminum nitride in said compact containing oxygen in an amount ranging from greater than about 1.0% by weight to less than about 4.5% by weight, and sintering said compact in a nitrogen-containing nonoxidizing atmosphere at a temperature ranging from about 1800° C. to about 2050° C. producing said polycrystalline body, said nitrogen-containing atmosphere containing sufficient nitrogen to prevent significant weight loss of said aluminum nitride.