Influence of scandium doping on temperature dependences of photochromic absorption of sillenites

Single crystals of scandium doped germanium sillenite (BGO:Sc) were obtained by the Czochralski method. The absorption and photochromic spectra were investigated as a function of temperature. For comparison the same spectra for nominally pure crystals were measured too. Scandium doping influences significantly on spectral dependences only at about 8000 cm-1. But the presence of Sc ions modifies strongly the temperature dependences of spectra. The characteristic photochromic temperature T0 for BGO:Sc is determined to be about 100 K. This value is higher than T0 for pure material. The main part of the photochromic spectrum is divided into 4 absorption bands (at 8350, 11660, 18090, 21350 cm-1). The fifth band is in the UV and it was not investigated in this paper. On the base of different temperature dependences the above four absorption bands are attributed to two centers.