Influence of Al~(3+) and P~(5+) ion contents on the valence state of Yb~(3+) ions and the dispersion effect of Al~(3+) and P~(5+) ions on Yb~(3+) ions in silica glass

摘要

Three series of Yb~(3+)-doped silica glasses containing different amounts of Al2O3 and P2O5 were prepared successfully by using a sol-gel method. Absorption, excitation and fluorescence spectra of Yb~(2+) ions in these silica glasses as well as X-ray photoelectron spectra (XPS) of Yb4d were recorded and analysed systematically. It is found out that the addition of Al~(3+) or P~(5+) ions has great influence on the redox state of ytterbium ions. With increasing Al~(3+) ion contents in these silica glasses, more trivalent Yb~(3+) ions are reduced to divalent Yb~(2+). In contrast, the increase of P~(5+) ion contents greatly promotes divalent Yb~(2+) ions to be oxidized to trivalent Yb~(3+). The possible redox mechanisms have been explored and discussed in detail. The influence of Al~(3+) and P~(5+) ion contents on the near-infrared luminescence intensity of Yb~(3+) ions and cooperative luminescence of Yb~(3+) ion pairs was also discussed. Both the near-infrared luminescence intensity of Yb~(3+) ions and cooperative luminescence of Yb~(3+) ion pairs decrease gradually with increasing Al~(3+) and P~(5+) ion contents. The decrease of cooperative luminescence of Yb~(3+) ion pairs indicates a good dispersion effect of Al~(3+) and P~(5+) ions on Yb~(3+) ions in Yb~(3+)-doped silica glass. The results are useful for optimization of fabrication of the high quality Yb~(3+)-doped silica fiber by the composite design of Yb-Al-P co-doped silica glass.