Characterization of the Cotunnite‐Type Phases of Zirconia and Hafnia by Neutron Diffraction and Raman Spectroscopy

Abstract

The crystal structures of the cotunnite‐type phases (space group, Pnam, Z = 4) of pure zirconia and hafnia prepared under high‐temperature, high‐pressure conditions in a multianvil device were refined by time‐of‐flight neutron powder diffraction. The structures of both compounds are very similar and the nine polyhedral metal‐oxygen distances range from 2.133(1) to 2.546(1) Å in ZrO 2 and from 2.121(1) to 2.535(2) Å in HfO 2 . The Raman spectra of both phases resemble one another strongly and are consistent with the cotunnite‐type structure. These results confirm that ZrO 2 and HfO 2 undergo transitions to the same phase at high pressure.