Graphite resistive heated diamond anvil cell for simultaneous high-pressure and high-temperature diffraction experiments

Abstract

High-pressure and high-temperature experiments using a resistively heated diamond anvil cell have the advantage of heating samples homogeneously with precise temperature control. Here, we present the design and performance of a graphite resistive heated diamond anvil cell (GRHDAC) setup for powder and single-crystal x-ray diffraction experiments developed at the Extreme Conditions Beamline (P02.2) at PETRA III, Hamburg, Germany. In the GRHDAC, temperatures up to 2000 K can be generated at high pressures by placing it in a water-cooled vacuum chamber. Temperature estimates from thermocouple measurements are within +/−35 K at the sample position up to 800 K and within +90 K between 800 and 1400 K when using a standard seat combination of cBN and WC. Isothermal compression at high temperatures can be achieved by employing a remote membrane control system. The advantage of the GRHDAC is demonstrated through the study of geophysical processes in the Earth’s crust and upper mantle region.

A role for subducting clays in the water transportation into the Earth’s lower mantle

“…Simultaneous P-T condition was created by using external resistive electrical heaters (a graphite foil heater (at PETRA-III) and a coil heater (at PLS and APS) surrounding the diamond anvils). The RH-DAC setup offers the advantage of providing homogeneous and stable temperature across the entire sample chamber 63 . During the experiment, we followed the P-T conditions proposed for the South Mariana-Kermadec subduction and Izu-Bonin subduction models to simulate the coldest and moderately cold subduction geotherms, respectively 35 .…”

“…Temperature was monitored using a R-type or K-type thermocouple attached to the pavilion of the diamond anvil close to the sample with the maximum uncertainties of ±3 °C. The overall uncertainty in the sample temperature has been estimated by the differences between the recorded thermocouple temperature and the calculated temperature based on the unit-cell volume and the known thermal expansion coefficient of standard materials 63 . The pressure was calculated using the equation of state of Au pressure marker 64,65 included in the sample chamber.…”

“…The pressure was calculated using the equation of state of Au pressure marker 64,65 included in the sample chamber. More detailed description of this type of RH-DAC setup can be found in the literature 63,66 . Initially, we compressed the sample to ~1.0-2.0 GPa and then increased the pressure and temperature in increments of ~0.5 GPa and 50 °C up to ~23 GPa and ~900 °C, respectively.…”