Synthesis, structural and photoluminescence characteristics of Dy³⁺/Eu³⁺ co-doped CaGdSbWO₈ phosphor for warm white LEDs

An elaborate study was performed on the Dy³⁺/Eu³⁺ ions co-doped CaGdSbWO₈ (CGSW) phosphor, prepared using a high temperature solid-state reaction method. The structural, morphological, elemental, and phase purity of the prepared phosphor samples were systematically analyzed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The XRD results for the CGSW phosphor showed good agreement with the standard JCPDS card no. #00-064-0231. Fourier Transform Infrared (FT-IR) spectroscopy was utilized to examine various vibrational bands present in the host lattice. The Tauc’s method was used to evaluate the optical energy band gap of the co-doped phosphors via diffuse reflectance spectra (DRS). The photoluminescence (PL) studies at 277 nm excitation wavelength show various emission peaks of the dopant (Dy³⁺ & Eu³⁺) ions. With increasing Eu³⁺ ions concentration, the peak intensities of Eu³⁺ ions increase while peak intensities of Dy³⁺ ions decrease, verifying energy transfer from Dy³⁺ to Eu³⁺ ions which was further confirmed using Reisfeld’s approximation. It was also observed that with increasing concentration of Eu³⁺ ions, the colour spectrum shifted from cool white to warm red region. The results of the current research are a welcome step in applicability of the Dy³⁺/Eu³⁺ co-doped CaGdSbWO₈ phosphor for UV excitable warm w-LEDs.