Modern techniques in measuring elasticity of Earth materials at high pressure and high temperature using ultrasonic interferometry in conjunction with synchrotron X-radiation in multi-anvil apparatus

In the past 6 years, state-of-the-art techniques have been developed for the studies of elastic properties of polycrystalline and single-crystal materials using simultaneous ultrasonic and X-ray diffraction techniques at high pressures and temperatures in multi-anvil apparatus. The capability of these techniques is illustrated using recent data for mantle phases such as forsterite, wadsleyite, CaSiO₃ perovskite, and (MgFe)O ferripericlase. Adaptation of the X-radiography technique enables direct measurements of sample length at high pressures and temperatures, enabling studies of unquenchable phases, liquids, and multi-phase aggregates. The use of dual-mode transducers produces P and S wave data at the same pressure and temperature conditions in a single acoustic experiment, thereby eliminating the uncertainties caused by the need for interpolating travel-time data to calculate the elastic wave velocities, and bulk and shear moduli at high pressure and temperature. Implementation of the transfer function method for travel-time measurements opens new opportunities for studying time-dependent processes using ultrasonic measurements, such as phase transformations and plastic deformation.