Phase Relations in the System ZrO2-Y2O3 at Low Y2O3 Contents

DTA with fired samples, and X-ray phase identification and lattice parameter techniques with quenched samples, have been used in a study of subsolidus phase relations in the low-Y2O3 portion of the ZrO2-Y2O3 system. It is found that, while about 1.5 percent Y2O3 is soluble in monoclinic ZrO2, a two-phase monoclinic solid solution-plus-cubic solid solution region reaches to about 7.5 percent Y2O3 below about 500 C. A two-phase tetragonal solid solution-plus-cubic solution exist in the 1.5-7.5 percent Y2O3 range over 500-1600 C; at higher Y2O3 compositions, cubic ZrO2 solid solution occurs.