Ti. Mah et al., HIGH-TEMPERATURE ENVIRONMENTAL STABILITY OF THE COMPOUNDS IN THE AL2O3-Y2O3 SYSTEM, Journal of the American Ceramic Society, 80(4), 1997, pp. 874-878
Heat treatments in several environments were performed on a series of
compounds in the Al2O3 and Y2O3 system: Al2O3-Y3Al5O12, eutectic, Y3Al
5O12, YAlO3, Y4Al2O9, and Y2O3, The yttrium aluminates were found to b
e stable at high temperatures under vacuum and in air. However, when t
hey were heat-treated under vacuum in proximity to SiC, degradation wa
s observed, This was found to be primarily a result of carbothermal re
duction, In a similarly reducing environment without Si, the yttrium a
luminates, acid Al2O3 and Y2O3, all exhibited degradation by carbother
mal reduction, Based upon the experimental results, a degradation mech
anism for yttrium aluminates was proposed.