High-pressure x-ray diffraction and Raman spectroscopy of HfV2O7 -: art. no. 214114

To study the pressure-induced changes of HfV2O7, energy dispersive synchrotron-based x-ray diffraction and Raman spectroscopy were performed up to 41.7 GPa and 59 GPa, respectively. X-ray diffraction indicates that HfV2O7 undergoes two phase transitions between 0 and 42 GPa, the first occurring at 3.7+/-0.3 GPa. The second is indicated by a gradual loss of the intensity of the Bragg peaks, suggesting pressure-induced amorphization, and is not complete even at 41.7 GPa. Using the Birch-Murnaghan equation of state to fit the x-ray diffraction data from the low-pressure phase, a bulk modulus of K=12.8+/-0.4 GPa and a pressure derivative of the bulk modulus, K'=4.0+/-0.5 is obtained for HfV2O7. Many of the Raman modes, which at zero pressure are manifolds of closely spaced peaks, separate when HfV2O7 is placed under pressure. Additionally, under compression there is a loss of the low wave number (200-550 cm(-1)) modes by 2.0+/-0.2 GPa, and at 4.7+/-0.3 GPa a loss of the high wave number modes (700-1000 cm(-1)).