Photoluminescent and structural properties of color tunable trivalent europium doped SrGdAlO₄ nanophosphors

A series of Eu³⁺ ion doped SrGdAlO₄ nanophosphors were prepared via solution combustion technique utilizing urea as a fuel. Structural properties of the tetragonal phase of the host/doped lattice belonging to the space group I4/mmm were characterized by powder X-ray diffraction (PXRD). Photoluminescence spectra, decay curves, UV–Visible diffuse reflectance spectra (UV–Vis DRS) and Judd–Ofelt analysis were utilized to characterize the photoluminescent properties. The radiative rates (A_r), branching ratios (B_r) and intensity parameters (Ω_λ) were estimated by Judd–Ofelt analysis. The optimal doping concentration of europium ions for SrGdAlO₄ host lattice was found to be 20 mol%, above which concentration quenching was observed due to dipole–dipole interactions. CIE coordinates values lie in the blue region at lower concentrations of Eu³⁺ ions, which shifted towards white and then to reddish-orange region with higher concentrations of Eu³⁺ ions, suggesting the color tunable property of the synthesized nanophosphors. Lower value of CCT and color tunable phenomenon proved it as potential candidate for warm white light and phosphor converted white light emitting diodes (Pc-WLEDs) applications. The optical band gap of both host lattice (5.50 eV) as well as of 20 mol% Eu³⁺ doped SrGdAlO₄ nanophosphors (5.26 eV) lie in the range of semiconductors which enhanced their areas of applications.