Electronic transitions in the VBO3 single crystal at high pressures

Optical absorption spectra of single crystals of the ferromagnetic semiconductor VBO₃ are studied at high pressures up to 70 GPa achieved in a diamond-anvil cell. An electronic transition accompanied by sharp changes in the optical parameters and a decrease in the optical gap from E ₀ = 3.02 eV to 2.25 eV is found at the pressure P _C ~ 30 GPa. The gap does not disappear in the high-pressure phase and its value becomes typical of semiconductors. This is indicative of a semiconductor-semiconductor transition. The transition to the metallic state may occur at the critical pressure P _met ≈ 290 GPa.