Effect of yttria and yttrium-aluminum garnet on densification and grain growth of alumina at 1200°-1300°C

Densification and grain growth of alumina were studied with yttria or yttrium-aluminum garnet (YAG) additives at the relatively low temperatures of 1200degrees-1300degreesC. Yttria doping was found to inhibit densification and grain growth of alumina at 1200degreesC and, depending on dopant level, had a lesser effect at 1300degreesC. At 1200degreesC, yttria inhibits densification more than it hinders grain growth. The rate of grain growth increases faster with temperature than the rate of densification. Alumina-YAG particulate composites were difficult to sinter, yielding relative densities of only 65% and 72% after 100 h at 1200degrees and 1300degreesC, respectively. Pure YAG compacts exhibited essentially no densification for times up to 100 h at 1300degreesC.