Influence of local phonon energy on quantum efficiency of Tb3+-Yb3+ co-doped glass ceramics containing fluoride nanocrystals

Abstract

The Tb3+ single-doped and Tb3+-Yb3+ co-doped glass ceramics with the precipitation of CaF2, CaF2-SrF2 solid state solution and SrF2 nanocrystals were designed and prepared by taking different amounts of CaF2 and SrF2 as the starting fluorides to investigate the influence of the crystalline phase on the total quantum efficiency. The formation of the fluoride nanocrystals and the incorporation of the doped rare earth ions into the fluoride nanocrystals were proved by the XRD measurement. The energy transfer from Tb3+ to Yb3+ was studied by the steady and time resolved spectra. The total internal quantum efficiencies were calculated based on the measured Tb3+ lifetime, which was about 10.5% improved in the SrF2 nanocrystals precipitated glass ceramics compared with that in the CaF2 nanocrystals precipitated glass ceramics mainly due to the lower phonon energy environment. Meanwhile, the total external quantum efficiencies were evaluated with the integrating sphere measurement system, which were 18.6%, 19.3% and 24.4%, respectively, for the CaF2, CaF2-SrF2 and SrF2 nanocrystals precipitated glass ceramics. Additionally, obvious difference between the calculated total internal quantum efficiency and the measured total external quantum efficiency was also discussed.