Green upconversion luminescence of Yb 3+ , Er 3+ co-doped NaLa(MoO 4 ) 2 phosphors

The upconversion (UC) luminescence properties of polycrystalline Er3+/Yb3+ co-doped NaLa(MoO4)(2) phosphors synthesized by a simple solid-state reaction method were investigated in detail. Under 980 nm excitation, Er3+/Yb3+ co-doped NaLa(MoO4)(2) exhibited weak red emissions near 660 and670 nm, and strong green UC emissions at 530 and550 nm corresponding to the intra 4f transitions of Er3+ (F-4(9/2), H-2(11/2), S-4(3/2)) -> Er3+ (I-4(15/2)). The optimum doping concentration of Er3+ and Yb3+ for highest emission intensity was determined by XRD and PL analysis. The Er3+/Yb3+ (7.0/10.0 mol%) co-doped NaLa(MoO4)(2) phosphor sample exhibited strongly shiny green emission. A possible UC mechanism for Er3+/Yb3+ co-doped NaLa(MoO4)(2) depending on the pump power dependence was discussed in detail.