Broad and intense NIR luminescence from rare earth doped SiO2-Nb2O5 glass and glass ceramic prepared by a new sol gel route

A new sol-gel route was used for obtaining Er3+/Yb3+ co-doped Nb2O5 nanoparticles distributed in a SiO2 based host. Phase separation and crystallization process were investigated for Er3+/Yb3+ co-doped nanocomposites at 70Si:30Nb molar ratio. X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Fourier transform infrared (FTIR), Raman, and Photoluminescence (PL) spectroscopy were used to assess the structural properties and their influence on luminescence. Amorphous Nb2O5 was identified after nanocomposite annealing at 700 °C, whereas at 900 °C and 1100 °C were identified both the orthorhombic and monoclinic phases. The average crystallite sizes were 6.6 nm at 900 °C and 16.4 nm at 1100 °C. Intense and broad NIR emission was observed for the nanocomposites annealed at 700 and 900 °C due to an efficient energy transfer from Yb3+ to Er3+ ions. Intense emissions at 980 nm and 1550 nm were also observed due to energy transfer from the host to Yb3+ and Er3+ ions, respectively. Additionally, a less efficient back energy transfer from Er3+ to Yb3+ ions was observed. The emission intensity and bandwidth were dependent on the nature of Nb2O5 crystalline phase, indicating that rare-earth (RE) ions are mostly distributed into Nb2O5 nanoparticles. The 4I13/2 and 2F5/2 excited state lifetimes were also dependent on Nb2O5 crystalline phase with shorter values for monoclinic Nb2O5. The featured luminescent properties exhibited by the rare earth-doped Nb2O5 make the nanocomposite materials potential candidates in many photonic applications.