Eu3+-Doped Fluorite-Type Molybdate Phosphors for Narrow-Band Red Emission with High Efficiency

Eu³⁺ is regarded as the most important red luminescent activator among rare earth ions. In this work, Eu³⁺-activated Gd₄MgMo₃O₁₆ nanophosphors were synthesized using the sol-gel method. The fluorite-type cubic structure of the material was unequivocally confirmed by XRD patterns and Rietveld structure refinements. A comprehensive investigation was conducted on the band width, intrinsic luminescence, and decay lifetime of the host material. The detailed luminescence transitions of Eu³⁺ activators in the Gd₄MgMo₃O₁₆ host are reported. The phosphor exhibited an extremely narrow luminescence line at 616 nm (corresponding to the ⁵D₀ → ⁷F₂ transition in Eu³⁺) with a full width at half maximum (FWHM) of approximately 1 nm. Its CIE chromaticity coordinates closely matched the NTSC standard for ideal red light. Based on the luminescence efficiency, the optimal Eu³⁺ doping concentration in the host is 40 mol%. The phosphor's excitation spectrum aligned well with the output emission wavelengths of commercial near-UV and blue LED semiconductor chips. Specifically, Gd_4-4xEu_4xMgMo₃O₁₆ (x = 0.4) has a maximum quantum efficiency (QE) of 70.5%, and exhibits high thermal ability, with an activation energy value of 0.437 eV. These characteristics render it particularly suitable for red-emitting applications in near-ultraviolet/blue GaN LED technologies.