ИСТИНА

Materials containing Bi-centers, which are characterized by 500 nm absorption band, and 1300 nm luminescence broad band, are promising candidates for lasers and fiber-optic amplifiers. To date these Bi-centers are considered as nanoclusters with a complex structure which includes 2 or more components: neutral Bi atoms, Bi3 -Bi2 dimers combined with a vacancy, Bi , Bi5 ions, etc. The glasses in the Bi2O3 concentration range of 5-50 mol%, including additionally doped with Cr2O3 as an oxidizer have been synthesized at 1050-1100?C and cooling with various rates. Optical and spectral-luminescent properties of glasses were investigated. Bi-centers concentration increased linearly with the Bi2O3 content in Cr-less glasses. The decrease of synthesis temperature or cooling rate led to Bi-centers content decrease. The addition of just 0.01 mol% Cr2O3 into the glass led to complete destruction of Bi-centers due to the oxidation-reduction interaction between Cr- and Bi- ions. Glasses' heat tre atment under various conditions was carried out. When treated in air a gradual discoloration of the samples was observed due to the oxygen diffusion into the glass. The original red color has been completely restored by re-sintering the clarified glass. All the processes of color change are described in terms of formation/destruction of optically active Bi-centers. This research was financially supported by the grant 17.1.18.0026.01 (10.4702.2017/BC).