Structural and Optical Studies of Bismuth Silicate Oxyfluoride Glasses for LED Applications.

The samples SBS20, SBS25 and SBS30 are prepared by traditional melt quenching method. The XRD pattern of prepared samples confirms the glassy nature and a broad peak at 2θ=28°. The Raman spectra indicate that addition of SrF2 into the glass matrix leads to loosening of network. It will create more non- bridging oxygen in the samples. The Absorption spectra shows two peaks at 466 nm and 499 nm due to Bi2+ in different environments. The absorption edge shifted to lower wavelength with lower content of Bi2O3 due to the less amount of Bi3+ ion in the glass matrix. Optical band gap increases from 2.84eV to 2.86eV with increasing the SrF2 content leads to loosening of network. Emission spectra consist of three peaks at 435 nm, 510 nm and 630 nm, blue region is arising from Bi3+ and other two are from Bi2+. 20SBS and 25SBS show white light whereas 30SBS shows yellowish green in CIE diagram. The color purity and correlated color temperature are also calculated. [ABSTRACT FROM AUTHOR]