摘要
Pressure-induced phase transition in magnesiochromite (MgCr2O4) was studied by in situ Raman spectroscopy and X-ray diffraction to 50 and 60 GPa, respectively. A polymorphic phase transition from cubic structure to tetragonal I41/amd structure was observed at pressures above 20 GPa and this transition is complete at 23.5 GPa. The volume data for magnesiochromite fitted to Birch-Murnaghan equation of state (EOS) yield K0 = 189(2) GPa, and V0 = 578.68(4) 脜3, consistent with theoretical calculations. The EOS of the high pressure tetragonal phase was also obtained as K0 = 191(8) GPa and V0 = 279(1) 脜3 when = 4 (fixed). The volume reduction at phase transition is about 4.4%. The high pressure phase is unquenchable and transformed back to magnesiochromite with little hysteresis upon release of pressure.