Phase Transformation at High Temperatures in Hafnia and Zirconia

Abstract

Phase transformation curves for HfO(2) and ZrO(2) have been made. Transformation hysteresis is discussed. The transformation of monoclinic to tetragonal as temperature increases occurs over the range 1000 degrees to 1200 degrees C in ZrO(2), and 1500 degrees to 1600 degrees C in HfO(2). With decreasing temperature the transition back to monoclinic occurs from 970 degrees to 750 degrees C in ZrO(2) and 1550 degrees to 1450 degrees C in HfO(2). These transformations have been visually observed in ZrO(2), but not in HfO(2).