Physical and luminescence properties of rare earth doped phosphate glasses for solid state lighting applications

Abstract

Luminescent glass for use in LED based lighting applications has recently attracted significant research interest. Samples of oxyfluoride phosphate glass doped with Dy₂O₃ and Eu₂O₃ were prepared using the conventional melt quenching process. The samples were studied through analysis of their density, molar volume, refractive index, absorption spectra, emission spectra, excitation spectra, decay time profile and by plotting their characteristics on a CIE diagram. It was found that the density of the glass samples produced increased with the concentration of ions in them. The absorption spectra for glass samples produced using both ions had clear absorption peaks. The excitation spectra that were found for NSDy and NSEu showed the strongest peaks at 350 and 393 nm respectively. It was thought that these peaks corresponded to the transition of ⁶H_15/2 and ⁷F₀ to the excited states ⁶F_11/2 + ⁶H_9/2 and ⁵L₆ respectively. The Judd-Ofelt (JO) theory was used to calculate the JO intensity parameters and radiative properties of the glass samples that were produced. The emission peaks that were observed at 573 nm for NSDy and 612 nm for NSEu show higher intensity than the other peaks. It was thought that these peaks corresponded to the transitions of ⁶H_13/2⁴F_9/2 and ⁵D₀⁷F₃ respectively. The CIE coordinates showed that the NSDy emits visible light in the white region and the NSEu emits visible light in the Reddish orange regions. It was concluded that both of the glass types produced could be good candidates for applications in the field of solid-state lighting and LEDs.