Green upconversion luminescence from poly-crystalline Yb 3+ , Er 3+ Co-doped CaMoO 4

The upconversion (UC) luminescence properties of polycrystalline Er3+/Yb3+ co-doped CaMoO4 synthesized by a complex citrate gel method were investigated in detail. Under 980nm excitation, Er3+/Yb3+ co-doped CaMoO4 has exhibited a weak red emission near 670nm and strong green UC emissions at 530 and 550nm, corresponding to the intra 4f transitions of Er3+ (4F9/2, 2H11/2, 4S3/2)→Er3+ (4I15/2). The optimum doping concentrations of Er3+ and Yb3+ were determined to result in the highest UC luminescence and a possible UC mechanism of Er3+/Yb3+ co-doped CaMoO4 depending on the pump power dependence is discussed in detail.