Near-infrared luminescent barium gallium-germanate glasses and glass-ceramics doped with bismuth

A series of barium gallium-germanate glasses (84-x) GeO2-14BaO-2Ga(2)O(3-x) Bi2O3 (x = 0; 0,1; 1; 3; 5 mol%) was synthesized by crucible technology. It was revealed that the appearance of a BaGe4O9 crystalline phase took place after additional thermal treatment of the glass samples. The structural and optical properties of the glasses and glass-ceramics were studied. It was shown that the spectral shapes and the peak positions of the absorption, luminescence and excitation bands strongly depend on the type of materials. In particular, the absorption band peaked at 480 and 660 nm is characteristic for the glass samples whereas in the absorption spectrum of the glass-ceramic two bands at 480 nm and 560 nm were observed. Moreover, with the appearance of a crystalline phase, the luminescence peak shifts towards shorter wavelengths, while its intensity increases. The possible states of Bi ions in the BaGe4O9 crystalline phase were calculated using a molecular cluster model. The obtained results indicate that an incorporated in the crystalline phase Bi+ ion could be considered as a possible near IR luminescence source.