Effect of oxygen on sintering of AlN

Abstract

The effect of the oxygen impurity on the densification behaviour of AlN was investigated. AlN powders containing different amounts of oxygen were synthesized from alumina and hot-pressed. The way in which oxygen accelerates densification is remarkable. Contrary to what is expected from the densification equation, the sintering rate decreases during the holding time at temperatures above 1900° C. This discrepancy is caused by the liberation of oxygen during the hot-pressing. The compression test, conducted on the hot-pressed specimens, shows that oxygen impurity also improves the mechanical strength of sintered AlN. The sintered specimens with more than 2.5 wt % of oxygen have compressive fracture stresses above 150kg mm⁻², which are adequate for a refractory material.