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 3rd‐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 3rd‐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.