Thermoelastic equation of state of boron suboxide B6O up to 6 GPa and 2700 K: Simplified Anderson-Gruneisen model and thermodynamic consistency

摘要

The p-V-T equation of state of superhard boron suboxide B6O has been measured up to 6 GPa and 2700 K using multianvil technique and synchrotron X-ray diffraction. To fit the experimental data, the theoretical p-V-T equation of state has been derived in approximation of the constant value of the Anderson-Gruneisen parameter delta (T) . Bulk modulus B (0) =181 GPa and its first pressure derivative B (0)' = 6 at 300 K; two parameters describing thermal expansion at 0.1 MPa, i.e., a = 1.4 x 10(-5) K-1 and b = 5 x 10(-9) K-2 as well as delta (T) = 6 have been included in the model. The good agreement between fitted and experimental isobars has been achieved to the absolute volume changes up to 5% as compared to the volume at standard conditions, V (0). The fitted thermal expansion at 0.1 MPa well consistent with the experimental data as well as with ambient-pressure heat capacity c (p) , bulk modulus B (0) and delta (T) describing its evolution with volume and temperature have been discussed. The fitted value of Gruneisen parameter gamma = 0.85 in agreement with previous empiric estimations for B6O and experimental values for other boron-rich solids has been reported.