A Single-Phased Emission-Tunable Phosphor Ca₉Y(PO₄)₇:Eu²⁺,Mn²⁺ with Efficient Energy Transfer for White-Light-Emitting Diodes

A series of single-composition emission-tunable Ca9Y(PO4)7:Eu2+,Mn2+ phosphors were synthesized by solid-state reaction. The energy transfer from Eu2+ to Mn2+ in Ca9Y(PO4)7 host matrix was studied and demonstrated to be a resonant type via a dipole−quadrupole mechanism with the critical distance of ∼ 11 Å. The wavelength-tunable white light can be realized by coupling the emission bands centered at 486 and 638 nm ascribed to the contribution from Eu2+ and Mn2+, respectively. By properly tuning the relative composition of Eu2+/Mn2+, chromaticity coordinates of (0.31, 0.33) can be achieved under excitation at 250−440 nm. Moreover, white-light-emitting diodes were fabricated through the integration of 365 nm chips and single composition white-light-emitting phosphors (Ca0.975Eu0.01Mn0.015)9Y(PO4)7 into a single package shows a cool white light of 7200 K, color rendering index of 76, and color coordinates of (0.30, 0.31) close to that of ideal white light can be achieved.