Influence of Crystallization on the Conversion of Sm3+→Sm2+ in SrO-Bi2O3-K2O-B2O3 Glass-Ceramics

Sm3+-doped glass 13SrO-2Bi(2)O(3)-5K(2)O-80B(2)O(3) was fabricated by the conventional melt-quenching technique. The glass-ceramics were obtained by heating the as-prepared glasses in air atmosphere at selected temperatures 550 degrees C, 600 degrees C, 615 degrees C, and 650 degrees C, respectively. The luminescence spectra of both Sm3+ and Sm2+ were detected in the ceramic heated at 650 degrees C where crystalline phase is formed. The as-prepared glass and the ceramics heated at 550 degrees C, 600 degrees C, and 615 degrees C show only the emission due to Sm3+. In the sample heated at 650 degrees C in air atmosphere, however, part of Sm3+ ions was converted to Sm2+, giving rise to sharp emission lines which are characteristic of Sm2+ in crystalline state. It is suggested that Sm2+ ions are located at Sr2+ site in the ceramic while Sm3+ ions are located at Bi3+ sites. The Sm2+-doped glass-ceramic has a high optical stability because the fluorescence intensity decreases by only about 8% of its initial value upon excitation at 488nm Ar+ laser.