Synthesis, Morphology and Concentration-Dependent Photoluminescence of Thermally Stable Dy³⁺ Activated Phosphor for...

Dysprosium ion-doped Calcium Yttrium Tungstate (Ca₃Y₂WO₉) (CaYW) phosphors were synthesised via the solid-state reaction method. The undoped and doped phosphor samples were characterised by the x-ray diffraction (XRD) method. The diffraction peaks of the samples, sintered at 1100 °C, matched well with reported Ca₃R₂WO₉-type patterns [1, 2], confirming the tetragonal crystal system. Scanning electron microscopy (SEM) was utilised to study the surface morphology of the samples. Diffuse reflectance spectroscopy (DRS) measured the optical band gap values. CaYW: xDy phosphors, with different doping concentrations of Dy³⁺ (x = 1.0, 3.0, 5.0, 7.0, 9.0, and 11.0 mol%), were synthesised, and their photoluminescence (PL) spectra were studied. No noticeable peak shifting with Dy³⁺ incorporation was observed, indicating retention of the host lattice structure. The emission spectra revealed that the phosphors, when excited at 352 nm, showed intense emission at 575 nm (yellow light), corresponding to the transition ⁴F_9/2→⁶H_13/2. Concentration quenching occurred after 9.0 mol% of Dy³⁺ ions, and thus, the optimum phosphor sample is CaYW:9.0Dy³⁺. For the prepared phosphor, the Commission Internationale de l'éclairage (CIE) coordinates were evaluated and were found in the yellowish-white region with the coordinates of the optimum sample equals to 0.3654, 0.3972. Fourier transform-infrared (FT-IR) spectra were analysed to identify the functional groups present in the samples. Thermogravimetric analysis (TGA) and temperature dependent-photoluminescence (TD-PL) analysis were also done to study the samples in a thermal context. In conclusion, the results of the current study demonstrate that the Dy³⁺ ions-doped CaYW phosphors may have the potential to be utilised in white light-emitting diodes (w-LEDs).