Determination of the charge state of chromium in Cr:Bi12GeO20 single crystals by spectral luminescence methods

The valence state and structural localization of Cr ions in Cr:Bi12GeO20 single crystals grown by the Czochralski method in air and annealed in argon or UV-irradiated have been determined in the spectral luminescence study. It is established that chromium is in the state of tetrahedrally coordinated Cr4+ ions in the samples studied. Octahedrally coordinated Cr2+ and Cr3+ ions and tetrahedrally coordinated Cr5+ ions were not revealed.