Site-occupancy, luminescent properties and energy transfer of a violet-to-red color-tunable phosphor Ca10Li(PO4)7: Ce3+, Mn2+

Abstract A series of color-tunable phosphors Ca 10 Li(PO 4 ) 7 : Ce 3+ , Mn 2+ were synthesized by high-temperature solid-state reaction. Site occupancy of Ce 3+ and Mn 2+ in Ca 10 Li(PO 4 ) 7 and corresponding luminescent properties were systemically studied. Rietveld refinement results indicate that the Ce 3+ ions are preferred to occupy 7-cooridnated M1 and M3 sites, and Mn 2+ ions are mainly occupying distorted octahedral M5 sites, which results in Ce 3+ violet emission at 370 nm and Mn 2+ red emission at 640 nm. The intensity of Mn 2+ red emission is greatly enhanced through efficient Ce 3+ -Mn 2+ energy transfer ( η ET =94%). The critical distance and corresponding mechanism of Ce 3+ -Mn 2+ energy transfer was found to be ~11 A and dipole-quadrupole interaction, respectively. The emitting colors of Ca 10 Li(PO 4 ) 7 : Ce 3+ , Mn 2+ phosphors can be tuned from violet through pink to red by adjusting the Ce 3+ /Mn 2+ ratio. The composition-optimized red phosphor Ca 10 Li(PO 4 ) 7 : 0.05Ce 3+ , 0.09Mn 2+ exhibits excellent thermal stability at high temperature (~100% at 160 °C).