The effect of SiO₂ crystallization in enhancing the luminescence of Dy³⁺-Sm³⁺ co-doped glass ceramics for cool white light application

The present work investigates the structural and luminescence behaviour of Dy³⁺-Sm³⁺ co-doped glass ceramics obtained through heat treatment of precursor glasses. The growth of SiO₂ polycrystalline particles and evolution of these crystallites in the glass domain are witnessed via XRD and FESEM study. The presence of network vibrational bands, hydroxyl groups and the increased quantity of bridging oxygens (BOs) in glass ceramics are analysed through FTIR spectroscopy study. The absorption study (UV-Visible-NIR) showed the possible electronic transitions of Dy³⁺ and Sm³⁺ ions. The red shift in the absorption band edges and the lower bandgap values are obtained as a result of improved heat treatment in glass ceramics. Emission studies show the enhanced luminescence intensity of glass ceramics under 350 and 402 nm excitations. Decay measurement of glass ceramics showed the improved lifetimes of Dy³⁺ and Sm³⁺ ions to have appeared in microseconds (×10^-6 s). The colour characteristics of glass ceramics analysed using CIE colour chromaticity diagram and correlated colour temperature (CCT) values suggest the neutral to cool white light emissions. Therefore, prepared glass ceramics with SiO₂ polycrystalline phase are considered to be suitable materials in cool white LEDs applications.