Calculation of Spectral Parameters for Doped/Codoped MWO4 (M = Ba2+/Ca2+) Phosphors

Abstract

We report the spectral parameters of Dy3+-doped and Sr2+/K+-codoped MWO4 (M = Ba2+/Ca2+) tungstate phosphors synthesized by solid-state reaction route. The structural and optical properties were investigated by x-ray diffraction (XRD) analysis, photoluminescence (PL) measurements, and ultraviolet–visible–near infrared spectroscopy. The XRD results indicate tetragonal structure of the phosphors in space group I4 1 /a. The PL spectra show blue and yellow emission at 489 nm and 577 nm, respectively, on excitation at wavelength of 350 nm. The diffuse reflectance spectra reveal bandgap values for the phosphors in the range from 4.24 eV to 5.7 eV. Judd–Ofelt theory was used to calculate the oscillator strength from the excitation spectra of the phosphors. The intensity parameters (Ω 2, Ω 4, and Ω 6) were used to calculate many radiative parameters such as the radiative transition probabilities (A R), radiative lifetime (τ R), branching ratio (β R), stimulated emission cross-section [σ(λ p)], and quantum efficiency (η) for certain excited states of Dy3+ ion.