Yb^3 + doped silica sol-gel glass powders were prepared with different concentrations of SiO₂, Al₂O₃ and P₂O₅ in order to understand the impact of the glass composition on the Yb^3 + emission properties. In this paper, we clearly show that not only the Al/P ratio but also the SiO₂ content have an impact on the Yb^3 +
spectroscopic properties. Our results provide new insight on the real
impact of the composition on the spectroscopic properties of Yb^3 + doped sol-gels: we demonstrate that an increase in the Al₂O₃ content at the expense of P₂O₅ leads to an increase in the intensity of the emission at 1000 nm of the Yb^3 + ions whereas an increase in the SiO₂ content decreases it. We clearly showed that the inexpensive sol-gel approach can be easily used when investigating new Yb^3 + doped silica glasses.