Warm to neutral white light emissions from Dy³⁺–Eu³⁺ co-doped glass ceramics containing NaBSiO₄ crystalline phase for W-LEDs applications

This paper reports on the structural, optical and luminescence studies of Dy³⁺–Eu³⁺ co-doped glass ceramics that are obtained via thermal treatment method. The initial confirmation on glass ceramics with the formation of NaBSiO₄ crystalline phase was made through XRD study. The FTIR study showed the vibrations of network formers (B₂O₃, SiO₂) and other functional groups. The quantity of non-bridging oxygens (NBOs) are increased in the glass ceramics with increase in annealing temperature. The absorption spectra (UV–visible-NIR) showed the possible transitions of Dy³⁺ and Eu³⁺ ions in the glass ceramics. A red-shift in the absorption band-edge and reduction in the optical band gap values were obtained for glass ceramics owing to their heating temperatures. Photoluminescence studies showed the excitations of Dy³⁺ and Eu³⁺ ions under 575 nm and 613 nm emission wavelengths. The obtained NaBSiO₄ crystalline phase in the glass ceramics has enhanced the luminescence intensity, and lifetimes of Dy³⁺ and Eu³⁺ ions compared to unheated precursor glass when excited under 350 nm and 393 nm. Color chromaticity diagram and correlated color temperature (CCT) values showed a shift in the color of light from warm white of precursor glass to neutral white of glass ceramics. The overall results justify the possibility of considering the Dy³⁺-Eu³⁺ co-doped glass ceramics as efficient materials for solid-state lighting applications like W-LEDs.