Bright and thermal-stable RGB emission realized by Eu2+-Tb3+/Mn2+ energy transfer in Na3SrMg11(PO4)9

•Structure, site-occupancy and luminescence of Na3SrMg11(PO4)9:Eu2+/Mn2+/Tb3+ were studied.•Broad excitation band and wide-gamut-coverage emission could be achieved by tuning Eu2+/Mn2+/Tb3+ ratio.•The optimal blue/green/red phosphors exhibit high quantum efficiencies with IQE>60%. [Display omitted] A series of tricolor-emitting fifillowite-structured Eu2+/Tb3+/Mn2+-doped Na3SrMg11(PO4)9 (NSMP) phosphors were synthesized. Its structural parameter, luminescent properties, and energy transfer behaviors were systematically studied. The optimal NSMP: Eu2+, Tb3+/Mn2+ phosphors exhibit bright RGB emission bands, i.e. blue emission from Eu2+, while green and red emission from sensitized Tb3+ and Mn2+, respectively. Eu2+-Tb3+/Mn2+ energy transfer processes are verified as a resonant type with ET efficiency of>80%. The emitting colors of NSMP: Eu2+, Tb3+, Mn2+ phosphors could be adjusted from blue (0.156, 0.077) to green (0.322, 0.552), to red (0.667, 0.299) by increasing Tb3+/Mn2+ doping content. The internal quantum efficiency of blue NSMP:0.04Eu2+, green NSMP:0.04Eu2+, 0.40Tb3+ and red NSMP:0.04Eu2+, 1.40Mn2+ phosphor is estimated at 64.46%, 78.17% and 78.03%, respectively. A significant leap of emission thermal-stability is found in Na3SrMg11(PO4)9: Eu2+ after co-activation with Mn2+/Tb3+ ions. In general, the emitting colors and energy transfer could be effectively regulated in the Na3SrMg11(PO4)9 host, and a general method for photoluminescence tuning is demonstrated.