Sr3La(PO4)3:Eu2+,Mn2+: A single-phased color-tunable phosphor and its energy transfer behavior

A series of novel Eu2+/Mn2+ co-doped color-tunable Sr3La(PO4)3 phosphors were synthesized by a high-temperature solid-state reaction. The photoluminescence properties and energy transfer process were investigated in detail. Two emission bands attributed to the Eu2+ and Mn2+ ions are observed under UV light excitation via an efficient energy transfer (ET) process. When the Eu2+ doping content is fixed, the emission chromaticity can be varied from blue to red by simply adjusting the content of Mn2+. The photoluminescence and lifetime analysis indicate that there is an efficient energy transfer from the Eu2+ to Mn2+ ions via a quadrupole-quadrupole mechanism with the critical distance of ~10 Å.