Effect of Li+ ions on the enhancement upconversion and stokes emission of NaYF4:Tb, Yb co-doped in glass-ceramics

Abstract

The glass ceramics samples with composition of 40SiO2–25Al2O3–18Na2CO3–10YF3–7NaF–0.5TbF3–1YbF3–xLi2CO3 (in mol%, x = 0, 1, 2, 3, 4, 5 and 6) were prepared using the conventional quenching techniques. The effect of the Li+ codoping on the enhancement upconversion (UC) and Stokes emission in Tb–Yb co-doped transparent glass-ceramics were investigated. Compared with the glass-ceramics sample without Li+ codoping, the UC and Stokes emission intensity of glass-ceramics samples with Li+ codoping were increased. Particularly, the green UC emission intensity band centered at 543 nm was strongly increased twice with the increase of Li+ up tp 4 mol%. Therefore, the Stokes emission results showed that the incorporation of Li+ ions into the NaYF4:Eu3+ lattice could induce a remarkable change of the Stokes emission intensity in red region (R = IED/IMD) with 393 nm excitation wavelength. It was indicated that it improved the effect of Li+ codoping in Tb–Yb on symmetry of the lattice. The possible mechanism responsible for the enhancement of UC and Stokes emission in Tb3+-Yb3+ co-doped were discussed.