Equation of state of cubic boron nitride at high pressures and temperatures

TL;DR

This study provides precise measurements of cubic boron nitride's equation of state at high pressures and temperatures, refining thermodynamic parameters and proposing a new pressure calibration method based on Raman spectroscopy.

Contribution

It offers the first comprehensive P-V-T data set for cubic BN up to 160 GPa and 900 K, and introduces a new pressure scale derived from Raman mode analysis.

Findings

Accurate EOS data up to 160 GPa and 900 K.

Refined thermodynamic parameters for cubic BN.

A new pressure calibration method based on Raman spectroscopy.

Abstract

We report accurate measurements of the equation of state (EOS) of cubic boron nitride by x-ray diffraction up to 160 GPa at 295 K and 80 GPa in the range 500-900 K. Experiments were performed on single-crystals embedded in a quasi-hydrostatic pressure medium (helium or neon). Comparison between the present EOS data at 295 K and literature allows us to critically review the recent calibrations of the ruby standard. The full P-V-T data set can be represented by a Mie-Gr\"{u}neisen model, which enables us to extract all relevant thermodynamic parameters: bulk modulus and its first pressure-derivative, thermal expansion coefficient, thermal Gr\"{u}neisen parameter and its volume dependence. This equation of state is used to determine the isothermal Gr\"{u}neisen mode parameter of the Raman TO band. A new formulation of the pressure scale based on this Raman mode, using physically-constrained parameters, is deduced.