Phase Transformation at High Temperatures in Hafnia and Zirconia

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Science  21 Jun 1963:
Vol. 140, Issue 3573, pp. 1330-1331
DOI: 10.1126/science.140.3573.1330


Phase transformation curves for HfO2 and ZrO2 have been made. Transformation hysteresis is discussed. The transformation of monoclinic to tetragonal as temperature increases occurs over the range 1000° to 1200°C in ZrO2, and 1500° to 1600°C in HfO2. With decreasing temperature the transition back to monoclinic occurs from 970° to 750°C in ZrO2 and 1550° to 1450°C in HfO2. These transformations have been visually observed in ZrO2, but not in HfO2.