  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-Gr\"uneisen parameter {\delta}T. The model includes bulk modulus B0
=181 GPa and its first pressure derivative B0' = 6 at 300 K; two parameters
describing thermal expansion at 0.1 MPa, i.e. a = 1.4x10-5 K-1 and b = 5x10-9
K-2, as well as {\delta}T = 6. The good agreement between fitted and
experimental isobars has been achieved to the absolute volume changes up to 5%
as compared to volume at standard conditions, V0. The fitted thermal expansion
at 0.1 MPa is well consistent with the experimental data, as well as with
ambient-pressure heat capacity cp, bulk modulus B0 and {\delta}T describing its
evolution with volume and temperature. The fitted value of Gr\"uneisen
parameter {\gamma} = 0.85 is in agreement with previous empiric estimations for
B6O and experimental values for other boron-rich solids.
