Single-phase tunable white-light-emitting Sr₃ La(PO₄)₃ : Eu²⁺, Mn²⁺ phosphor for white LEDs

A novel, near-ultraviolet-excited white-light-emitting phosphor Sr₃La(PO₄)₃:Eu²⁺, Mn²⁺ was synthesized by the solid-state method. Luminescence properties and the energy transfer mechanism were investigated in detail by photoluminescence spectra and decay curves. With the energy transfer between Eu²⁺ and Mn²⁺, a cold white light with chromaticity coordinates of (0.2790, 0.2273), correlated color temperature of 6501 K, Ra of 70, and external quantum efficiency of 35.5% was realized by changing the ratios of Eu²⁺ and Mn²⁺ in the Sr₃La(PO₄)₃:Eu²⁺, Mn²⁺ phosphors. Resonant energy transfer from Eu²⁺ to Mn²⁺  ions has been demonstrated to be a dipole-dipole mechanism in Sr₃La(PO₄)₃. The energy transfer efficiency increases with Mn²⁺ concentration increasing, and reaches a maximum of 55.6%.