Thermally stable luminescence and dosimetric features of Ho(III) activated tungstate double perovskite

Luminescent efficient tungstate double perovskites Ca<inf>3</inf>WO<inf>6</inf> doped with Ho³⁺ were synthesized via the solid-state reaction at 1200 C°. The resulting phosphors were analyzed using Rietveld refinement of X-ray diffraction (XRD) data, confirming a monoclinic crystal structure with crystallite sizes ranging between 50 and 55 nm. Optical bandgap determination was facilitated by diffusion reflectance spectra (DRS). Fourier transform infrared (FTIR) studies were conducted to identify functional group vibrations. The optical excitation of the Ca<inf>3</inf>WO<inf>6</inf>:Ho³⁺ phosphors under different excitation conditions resulted in intense green photoluminescence (PL) emission at 545 nm, indicative of the ⁵F<inf>4</inf>–⁵I<inf>8</inf> transition of Ho³⁺ ions. Thermal stability assessment of Ca<inf>3</inf>WO<inf>6</inf>:1 % Ho³⁺ phosphor under blue excitation (454 nm) revealed good thermally stable luminescence about 85.32 % at LED working temperature (150 °C). PL decay studies were conducted to analyze fluorescent behaviour, wherein by means of PL decay lifetime, the PL quantum efficiency of Ca<inf>3</inf>WO<inf>6</inf>:1 % Ho³⁺ phosphor is computed to be 91.1 %. The CIE color coordinates of the phosphors being investigated reside within the green spectral region, with a calculated color purity of 93.25 % observed for Ca<inf>3</inf>WO<inf>6</inf>:1%Ho³⁺. Furthermore, the phosphors under study exhibited high-quality thermoluminescence (TL) after beta irradiation. The detailed TL characterization conducted to assess dosimetric properties. The impact of Ho³⁺ concentrations and beta dose on TL intensity are two major aspects that have been investigated in detail. TL fading experiments were performed to determine dose storage capacity over a month after beta irradiation. Additionally, the various heating rate (VHR) experiments are conducted to determine the TL kinetic parameters. Besides, the glow curve deconvolution (GCD) for trap parameter determination is also applied, where the results obtained are comparable with the VHR results.