High thermal conductivity aluminum nitride ceramic body

Claim 1

A process for producing a polycrystalline body comprised of a composition defined and encompassed by line ABCDEFA but not including lines CD and EF of FIG. 1, a porosity of less than about 5% by volume of said body and a thermal conductivity greater than 1.0 W/cm·K at 22° C. which comprises forming a mixture comprised of aluminum nitride powder and an yttrium additive selected from the group consisting of yttrium, yttrium hydride, yttrium nitride and mixtures thereof, said aluminum nitride and yttrium additive containing oxygen, shaping said mixture into a compact, said mixture and said compact being comprised of a composition wherein the equivalent % of yttrium, aluminum, nitrogen and oxygen is defined and encompassed by line ABCDEFA but not including lines CD and EF in FIG. 1, said mixture, said compact and said polycrystalline body being comprised of from greater than about 1.6 equivalent % yttrium to about 19.75 equivalent % yttrium, from about 80.25 equivalent % aluminum up to about 98.4 equivalent % aluminum, from greater than about 4.0 equivalent % oxygen to about 15.25 equivalent % oxygen and from about 84.75 equivalent % nitrogen up to about 96 equivalent % nitrogen, and sintering said compact at a temperature ranging from about 1850° C. to about 2170° C. in an atmosphere at ambient pressure selected from the group consisting of nitrogen, argon, hydrogen and mixtures thereof to produce said polycrystalline body, said compact containing sufficient equivalent percent of yttrium and oxygen to form a sufficient amount of liquid phase at sintering temperature to densify the compact to produce said polycrystalline body, said sintering temperature being a sintering temperature for said compact.