The relationship between occupied sites and Mn2+ quantum efficiency in dual-emission Mg3Ca3(PO4)4: Eu2+, Mn2+ phosphors

• The relationship between occupied sites and Mn2+ quantum efficiency in Mg3Ca3(PO4)4: Eu2+, Mn2+ phosphors were discussed.
• The ion-size compensation effect leads to the formation of Eu2+–Mn2+ cluster and efficient Eu2+ → Mn2+ energy transfer.
• Emission color can be tuned from blue to pink by adjusting Eu2+/Mn2+ ratio.

Dual-emitting Eu2+ and Mn2+ codoped Mg3Ca3(PO4)4 phosphors have been synthesized, and energy transfer process from Eu2+ to Mn2+ was studied. The relationship between Eu2+ → Mn2+ energy transfer efficiency (ηT) and Mn2+ quantum efficiency (QE) with different Mn2+ occupied sites were compared and discussed. The ion-size compensation effect when Eu2+/Mn2+ occupying Ca2+ sites leads to the formation of Eu2+–Mn2+ cluster, which benefits the effective Eu2+ → Mn2+ energy transfer and efficient Mn2+ sensitized emission. The emission color of the phosphor can be tuned from blue to near-white and eventually to pink by adjusting the contents of Eu2+ and Mn2+. The Mn2+ emission wavelength red-shifts with increasing Mn2+ content, which is attributed to photon reabsorption process. The results indicated that Mg3Ca3(PO4)4: Eu2+, Mn2+ may serve as a potential color-tunable phosphor for NUV LED.