The role of Yb3+ concentrations on Er3+ doped SrLaMgTaO6 double perovskite phosphors

Er3+, Yb3+ co-doped SrLaMgTaO6 phosphors have been synthesized by a solid state reaction method. Under a 975 nm excitation, the SrLaMgTaO6: Er3+/Yb3+ phosphors exhibited strong green luminescence centered at 525 nm and 545 nm and relatively weak red anti-stokes luminescence centered at 660 nm. Herein, we have established the upconversion mechanism based on the down conversion and upconversion photoluminescence (UCPL) properties. The sensitized energy upconversion [s-ETU2: Yb3+ (F-2(5/2)) + Er3+ (I-4(11/2)) -> Yb3+ (F-2(7/2)) + Er3+ (F-4(7/2))] is a main route of green UCPL, and the energy back transfer [EBT: Er3+ (S-4(3/2)) + Yb3+ (F-2(7/2)) -> Er3+ (I-4(13/2)) + Yb3+ (F-2(5/2))] is a main route of red UCPL, which reduces the green UCPL to a certain degree. The reduced green and red UCPL of the sample with a high concentration of Yb3+ is mainly attributed to the concentration quenching of the Yb3+ ion.