Phase Relations and Ordering in the Systems MgO‐Y ₂ O ₃ ‐ZrO ₂ and CaO‐MgO‐ZrO ₂

Abstract

The phase relations in the systems MgO‐Y 2 O 3 ‐ZrO 2 and CaO‐MgO‐ZrO 2 were established at 1220° and 1420°C. The system MgO‐Y 2 O 3 ‐ZrO 2 possesses a much‐larger cubic ZrO 2 solid solution phase field than the system CaO‐MgO‐ZrO 2 at both temperatures. The ordered δ phase (Zr 3 Y 4 O 12 ) was found to be stable in the system ZrO 2 ‐Y 2 O 3 at 1220°C. Two ordered phases φ 1 (CaZr 4 O 9 ) and φ 2 (Ca 6 Zr 19 O 44 ) were stable at 1220°C in the system ZrO 2 ‐CaO. At 1420°C no ordered phase appears in either system, in agreement with the previously determined temperature limits of the stability for the δ, φ 1 , and φ 2 phases. The existence of the compound Mg 3 Y z O 6 could not be confirmed.