Development of Li₂O-SrO-GdF₃-B₂O₃ oxyfluoride glass for white light LED application

Dysprosium doped Li₂O-SrO-GdF₃-B₂O₃ (LSGB) glasses were prepared by the conventional melt quenching technique in order to study the luminescence properties and their utility for white light emitting diodes (LEDs). The glass structure was studied by X-ray diffraction (XRD) and Fourier transform infra-red (FT-IR) spectroscopy. XRD confirmed the amorphous structure of the glass samples. The FT-IR spectra revealed the presence of BO₃, BO₄ and non-bridging oxygen's. The optical absorption measurement were carried out in UV-VIS-NIR region. The PL emission and excitation spectra for the LSGB glasses were investigated. From the excitation and the emission spectra the highest Dy³⁺ excitation and emission intensities was observed for 0.5 mol% Dy³⁺-doped oxyfluoride glass. Strong blue (482 nm) and yellow (575 nm) emission bands were observed upon various excitations. These two emissions corresponds to the (⁴F_9/2 → ⁶H_15/2) and (⁴F_9/2 → ⁶H_13/2) transitions of Dy³⁺ ions, respectively. The blending of these blue and yellow bands gives white light. The CIE 1931 chromaticity coordinates for all the as made glass samples under various excitation wavelengths lies right in white region. The calculated correlated color temperature (CCT) values for the present oxyfluoride glasses were found in the range of 4336–4299 K. These were slightly more than warm CCT (i.e., CCT<4000 K) which lies in between those of fluorescent tube (3935 K) and day light (5500 K). These results reveals the possibility of the studied glasses to be used in various photonic devices for white light generation.