Pressureless sintering process to produce high thermal conductivity

Abstract

A process for producing an aluminum nitride ceramic body having a composition defined and encompassed by polygon LT1DM but not including lines LM and DM of FIG. 4, a porosity of less than about 10% by volume, and a thermal conductivity higher than 1.00 W/cm.multidot.K at 25.degree. C. which comprises forming a mixture comprised of aluminum nitride powder containing oxygen, yttrium oxide, and free carbon, shaping said mixture into a compact, said mixture and said compact having a composition wherein the equivalent % of Yttrium and aluminum ranges from point T1 up to point M of FIG. 4, said compact having an equivalent % composition of Y, Al, O and N outside the composition defined and encompassed by polygon LT1DM of FIG. 4, heating said compact to a temperature at which its pores remain open reacting said free carbon with oxygen contained in said aluminum nitride producing a deoxidized compact, said deoxidized compact having a composition wherein the equivalent % of A1, Y, O and N is defined and encompassed by polygon LT1DM but not including lines LM and DM of FIG. 4, and sintering said deoxidized compact at a temperature of at least about 1855.degree. C. producing said ceramic body.