Thermal equation of state of cubic silicon carbide at high pressures

Abstract

We have performed in situ X-ray diffraction measurements of cubic silicon carbide (SiC) with a zinc-blende crystal structure (B3) at high pressures and temperatures using multi-anvil apparatus. The ambient volume inferred from the compression curves is smaller than that of the starting material. Using the 3^rd -order Birch-Murnaghan equation of state and the Mie-Grüneisen-Debye model, we have determined the thermoelastic parameters of the B3-SiC to be K₀ =228±3 GPa, K₀ ',=4.4±0.4, q=0.27±0.37, where K₀ , K₀ ' and q are the isothermal bulk modulus, its pressure derivative and logarithmic volume dependence of the Grüneisen parameter, respectively. Using the 3^rd -order Birch-Murnaghan EOS with the thermal expansion coefficient, the thermoelastic parameters have been found as K₀ =221±3 GPa, K₀ ',=5.2±0.4, α₀ =0.90±0.02 ⋅ 10^-5 ⋅ K^-1 , where α₀ is the thermal expansion coefficient at room pressure and temperature. We have determined that paired B3-SiC - MgO calibrants can be used to estimate pressure and temperature simultaneously in ultrahigh-pressure experiments up to 60 GPa.

Keywords: Equation of state; High pressure; Multi-anvil apparatus; Silicon carbide; Synchrotron.