Cubic boron nitride as a primary calibrant for a high temperature pressure scale

Abstract

We present results establishing a new high pressure scale at high temperature based on the thermal equation of state and elastic properties of cubic boron nitride (cBN). This scale is derived from simultaneous measurements of density and sound velocities at high pressure and temperature independent of any previous pressure scale. The present results obtained at room temperature to 27 GPa suggest the validity of the current ruby scale (within±4% at 100 GPa). At high temperature, data obtained at 16 GPa to 723 K are in fair agreement with the thermal equation of state of cBN reported in our previous work. We have also shown that cBN can serve as a convenient pressure gauge in X-ray and optical studies using the laser heated diamond anvil cell.

Keywords:

• Cubic BN
• Brillouin spectroscopy
• Equation of state
• High-pressure scale

Acknowledgements

We are grateful to A. Bliss at LLNL for polishing our cBN samples and also Barry Olsen for high temperature vacuum annealing efforts. The work at LLNL was performed under the auspices of the US Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No.W-7405-Eng-48. Synchrotron X-ray diffraction and Brillouin spectroscopy were performed at GSECARS (APS, supported by DOE Contract No. W-31-109- Eng-38). This research was partially supported by National Science Foundation under grant EAR 01-35642 (to JDB), which provided funds for the construction of the Brillouin facility at Sector 13 of the APS, and support for this particular study.