Efficient visible-emitting Sm ³⁺ - and Pr ³⁺ -doped Sr ₉ MgK(PO ₄ ) ₇ phosphors: spectroscopic and Judd–Ofelt analysis

Sm3+- and Pr3+-activated Sr9MgK(PO4)7 phosphors were synthesized via a wet chemical route and systematically investigated for their structural and photoluminescence properties. Phase purity and morphology were confirmed using XRD and SEM analyses, while EDS verified the elemental composition. The photoluminescence spectra exhibited characteristic orange–red emission for Sm3+ and multicolor emission for Pr3+, arising from their intrinsic 4f–4f transitions. An optimal dopant concentration of 0.8 mol% was identified, beyond which concentration quenching occurred due to multipolar interactions. Furthermore, Judd–Ofelt analysis was performed to evaluate the local environment and radiative properties of the rare-earth ions. The relatively high Ω2 values suggest a low-symmetry and moderately covalent environment, while the calculated radiative lifetimes confirm efficient radiative relaxation. These results demonstrate that Sr9MgK(PO4)7 is a promising host for rare-earth-activated phosphors for solid-state lighting applications.