SYNTHESIS,MORPHOLOGY AND LUMINESCENT PROPERTIES OF Ca3Y2WO9:Dy3+ PHOSPHORS FOR W-LED APPLICATIONS

Abstract

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 1100ºC, closely resembled the Joint Committee on Powder Diffraction Standards (JCPDS) pattern with card number 00-038-0218, and the crystal system was found to be tetragonal. 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:xDy3+ phosphors, with different doping concentrations of Dy3+ (x=1, 3, 5, 7, 9, and 11 mol%), were synthesised, and their photoluminescence (PL) spectra were studied. The emission spectra revealed that the phosphors, when excited at 352 nm, showed intense emission at 575 nm (yellow light), corresponding to the transition 4F9/2→6H13/2. Concentration quenching occurred after 9 mol% of Dy³⁺ ions, and thus, the optimum phosphor sample is CaYW: 9mol% Dy3+. For all the samples of the phosphor, the Commission Internationale de l'éclairage (CIE) coordinates were evaluated, and they were found in the yellowish-white region. The coordinates for the optimum sample were (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).