Abstract
In situ x-ray diffraction and Raman spectroscopy have been carried out to pressures of 93.6 and 63.2 GPa, respectively, to explore the pressure-induced phase transformation of spinel. adopts a distorted tetragonal spinel structure at one atmosphere. At a pressure of ∼32.5 GPa, both x-ray diffraction and Raman spectroscopy indicate that transforms to the orthorhombic structure, which remains stable to at least 93.6 GPa. The bulk modulus of the tetragonal and the high-pressure polymorphs were calculated to be 94(12) and 145(16) GPa, respectively, with Upon release of pressure the orthorhombic phase persists and appears to be structurally metastable. At zero pressure, laser induced heating leads to a significant transformation back to the tetragonal phase. The high-pressure orthorhombic phase at one atmosphere is 14.7% denser than the tetragonal phase.
- Received 28 April 2003
DOI:https://doi.org/10.1103/PhysRevB.68.094101
©2003 American Physical Society