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

Highlights: • 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. - Abstract: 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 (η_T) 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