Investigations on luminescence of Ca8MgGd(PO4)7:Eu2+, Mn2+, Yb3+, Er3+, Ho3+, Tm3+ phosphors

Abstract To explore new emission-tunable phosphors with down-shifting and up-conversion properties, a series of Ca8MgGd(PO4)7:Eu2+, Mn2+ and Ca8MgGd(PO4)7:Yb3+, Er3+, Ho3+, Tm3+ samples were synthesized by solid-state reaction method, and their photoluminescence properties were studied. For down-shifting, Eu2+-single-doped Ca8MgGd(PO4)7 exhibits a very broad yellow–white emission from 400 to 800 nm upon 365 nm excitation, which originates from various Eu2+ emission centers. When the Mn2+ is introduced into Ca8MgGd(PO4)7:Eu2+, an extremely efficient energy transfer from Eu2+ to Mn2+ occurs and decreases the Eu2+ emission intensity strongly. The corresponding energy transfer efficiencies were evaluated from the decay curves. For different Mn2+ concentrations, the emitting light colors can be tuned conveniently and red emission is obtained finally. For up-conversion, the red, green, and blue tri-color emissions upon 980 nm excitation have been gained in the Yb3+–Ho3+, Yb3+–Er3+, and Yb3+–Tm3+ doped Ca8MgGd(PO4)7, respectively. By varying the relative concentrations of Yb3+, Er3+, Ho3+, and Tm3+, tunable emission was realized upon near-infrared excitation, and an efficient energy transfer from Tm3+ to Er3+ has been found in the Yb3+–Er3+–Tm3+ tridoped Ca8MgGd(PO4)7 samples.