Analysis of Judd–Ofelt parameters and radioluminescence results of SrNb2O6:Dy3+ phosphors synthesized via molten salt method

Abstract

In this work, Dy³⁺-doped SrNb₂O₆ phosphors were fabricated by the molten salt process, which avoids high sintering temperatures, prolonged reaction time and poor compositional homogeneity. All samples crystallized to the orthorhombic columbite structure with space group, P21/c, while a rod-like morphology was observed by scanning electron microscopy (SEM). PL (photoluminescence) and RL (radioluminescence) spectra of SrNb₂O₆:Dy³⁺ exhibited a strong blue emission peak at 576.0 nm related to ⁴F_9/2 → ⁶H_15/2 transition of Dy. The high RL emission of the ⁴F_9/2 → ⁶H_15/2 (electric dipole) transition upon X-ray-induced excitation led to a decrease in Dy³⁺ local environmental symmetry. The Judd–Ofelt (J–O) theory was applied to the PL excitation spectra for the calculation of optical data such as Ω₂, Ω₄, and Ω₆ parameters, radiative transition probability (A_r), branching ratios (β, β_exp) and stimulated emission cross-section (σ_e). The quantum efficiencies (η_QE) varied between 35.47 and 31.93%, which are compatible with theoretical quantum efficiencies based on the Einstein relation. The CIE chromaticity coordinates (x, y) and CCT (correlated color temperature) parameter for 3 mol% phosphor were defined (0.385, 0.432) and 4209 K, respectively.