Equation of state of scheelite-structured ZrGeO4 and HfGeO4

The high-pressure behaviour of scheelite-structured ZrGeO4 and HfGeO4 has been investigated with the help of angle-dispersive powder x-ray diffraction measurements. Our results show that these compounds do not undergo any phase transition up to the pressures of 20.7 and 19.0 GPa, respectively. The isothermal bulk modulus and its pressure derivatives are found to be 238 GPa and 4.5 for ZrGeO4, and 242 GPa and 4.8 for HfGeO4, implying that these germanates are highly incompressible.