NEW HIGH-PRESSURE PHASE OF ZRO2 ABOVE 35-GPA

Phase transformations of pure ZrO2 at high pressure up to 60 GPa were investigated by using x-ray diffraction and micro-Raman-scattering methods. The existence of phase transformation at about 13 GPa was reconfirmed by the spectral change of in situ Raman scattering. A new phase transformation at 35 GPa was observed from both of the experimental methods employed. A new high-pressure phase is stable up to 60 GPa and quenchable to ambient conditions. The measured x-ray diffraction pattern for this high-pressure phase was indexed on the basis of tetragonal symmetry. Eight Raman bands were observed for the quenched high-pressure phase. Candidate space groups that are consistent with the obtained experimental results were deduced. The most plausible space group is considered as one of C4h1, C4h4, D4h1, or D4h5 (P4/m, P42/n, P4/mmm, or P4/mbm). The molar volume for the new high-pressure phase is smallest in the high-pressure phases so far reported for ZrO2.. AE © 1990 The American Physical Society.