Phase Relations in the System ZrO 2‐ Y 2 O 3 at Low Y 2 O 3 Contents

Subsolidus phase relations in the low‐Y 2 O 3 portion of the system ZrO 2‐ Y 2 O 3 were studied using DTA with fired samples and X‐ray phase identification and lattice parameter techniques with quenched samples. Approximately 1.5% Y 2 O 3 is soluble in monoclinic ZrO 2 , a two‐phase monoclinic solid solution plus cubic solid solution region exists to ∼7.5% Y 2 O 3 below ∼500°C, and a two‐phase tetragonal solid solution plus cubic solid solution exists from ∼1.5 to 7.5% Y 2 O 3 from ∼500° to ∼1600°C. At higher Y 2 O 3 compositions, cubic ZrO 2 solid solution occurs.