X-ray analysis and optical studies of Dy³⁺ doped NaSrB₅O₉ microstructures for white light generation

Highlights: • NaSrB₅O₉:Dy³⁺ microstructures were synthesized by solid state reaction. • Crystallite size and lattice strain was estimated by W–H analysis. • Plate-like morphology with monoclinic structure is identified by SEM images. • Highest lifetimes of 931 μS were obtained for this system. - Abstract: A white light emitting phosphor NaSrB₅O₉:Dy³⁺ was synthesized by a conventional solid state reaction method. The structure of the phosphors was analyzed by powder X-ray diffraction (XRD), revealing that the phosphors crystallized in monoclinic crystal structure with the space group (P2₁/c). Williamson–Hall (W–H) analysis was used to study the individual contributions of crystallite sizes and lattice strain on the peak broadening of NaSrB₅O₉:Dy³⁺ phosphors. Monoclinic microstructures of nearly plate-like morphologies were observed in the FE-SEM images. Upon near-UV excitation wavelength (390 nm), the blue emission at ∼482 nm (⁶H_15/2) and yellow emission at ∼584 nm (⁶H_13/2) were observed in the phosphors. The critical quenching concentration of Dy³⁺ in NaSrB₅O₉ phosphor was found to be 3 at.% with the critical distance (R_c) of ∼22.30 Å and the corresponding concentration quenching mechanism was testified to be the exchange interaction between the dopant Dy³⁺ ions. In order to investigate the application in white LEDs, the Commission International de l'Eclairage (CIE) chromaticity coordinates, color temperature and decay curve measurements of Dy³⁺ ions doped NaSrB₅O₉ phosphors were carried out. The yellow to blue (Y/B) emission integrated intensity ratio is maximum (∼0.9) for all the concentrations, suggesting that the phosphors favor for white illumination