Photoluminescent properties and Judd-Ofelt analysis of Eu³⁺-doped NaMg(PO₃)₃ red phosphor

A series of novel red-emitting Na_1-xMg(PO₃)₃: xEu³⁺ phosphors were successfully synthesized using the high-temperature solid-state method. The crystal structure, photoluminescence spectra, decay lifetime and quantum efficiency of the phosphors were investigated as a function of Eu³⁺ concentration. A dominant red emission peak centered at 612 nm along with an intense ⁵D₀→⁷F₄ transition at 699 nm indicates that Eu³⁺ occupies low symmetry sites in NaMg(PO₃)₃ host lattice, which was confirmed by Judd-Ofelt analysis. The crystallographic site-occupations of Eu³⁺ were investigated by the site-selective excitation and emission spectra in the ⁵D₀→⁷F₀ region, which indicates that Eu³⁺ ion in NaMg(PO₃)₃ prefers to occupy the crystallographic site of C₃ symmetry. The emission intensity is closely dependent on Eu³⁺ concentration with critical concentration of 8 mol%. NaMg(PO₃)₃: Eu³⁺ phosphor exhibits good thermal stability (67.2% at 473 K).