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 K 0 =228±3 GPa, K 0 ’ ,=4.4±0.4, q =0.27±0.37, where K 0 , K 0 ’ 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 K 0 =221±3 GPa, K 0 ’,=5.2±0.4, α 0 =0.90±0.02 ⋅ 10 −5 ⋅ K −1 , where α 0 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.