Search

Resistive heating of a sample in a diamond anvil cell (DAC) can generate a homogeneous temperature field across the sample chamber with reliable temperatures measured by a thermocouple. It is of importance in experiments aiming at exploring phase diagrams and quantifying thermoelastic properties of materials. Here, we present a ring-heater design developed for BX90 diamond anvil cells (DACs). It is made of a ring-shaped aluminum oxide holder hosting a tungsten wire coil inside and coupled with Ar + 2% H2 gas to prevent oxidation during experiment. This modular plug-and-play design enables in situ studies of samples via x-ray diffraction up to a temperature of 1700K. Temperature in the BX90 sample volume as measured through a thermocouple was calibrated using the melting point of gold. As an application of this design, we report the thermal expansion coefficient of MgO at 9.5(1) GPa.

We observe that pressure-induced amorphization of Ga2SeTe 2 (a III-VI semiconductor) is directly influenced by the periodicity of its intrinsic defect structures. Specimens with periodic and semi-periodic two-dimensional vacancy structures become amorphous around 10-11 GPa in contrast to those with aperiodic structures, which amorphize around 7-8 GPa. The result is an instance of altering material phase-change properties via rearrangement of stoichiometric vacancies as opposed to adjusting their concentrations. Based on our experimental findings, we posit that periodic two-dimensional vacancy structures in Ga2SeTe2 provide an energetically preferred crystal lattice that is less prone to collapse under applied pressure. This is corroborated through first-principles electronic structure calculations, which demonstrate that the energy stability of III-VI structures under hydrostatic pressure is highly dependent on the configuration of intrinsic vacancies. © 2014 AIP Publishing LLC.