摘要
BaCrO 4 was studied to 25 GPa in a diamond-anvil cell using both Raman spectroscopy and x-ray diffraction methods. Our results showed that BaCrO 4 exhibits a phase transition near 9 GPa from both Raman and x-ray diffraction measurements. The new high-pressure phase (BaCrO 4 -II) is suggested as a monoclinic (P2 1 /m) structure, different from other high-pressure forms of ABO 4 -type compounds. Moreover, the high-pressure phase of BaCrO 4 is found to be reversible; the low-pressure phase is recovered at ∼8 GPa upon decompression. The pressure-volume data of BaCrO 4 fitted to a third-order Birch-Murnaghan equation of state yield a bulk modulus of 53(1) GPa and a pressure derivative of 6.8(5), in agreement with the theoretical prediction. For the high-pressure phase BaCrO 4 -II, the bulk modulus is 117(10) GPa and the pressure derivative is 3(1). © 2010 The American Physical Society.