This paper reports on the preparation of novel sol-gel erbium-doped SiO
2-based nanocomposites embedded with Nb
2O
5 nanocrystals fabricated using a bottom-up method and describes their structural, morphological, and luminescence characterization. To prepare the glass ceramics, we synthesized xerogels containing Si/Nb molar ratios of 90:10 up to 50:50 at room temperature, followed by annealing at 900, 1000, or 1100 °C for 10 h. We identified crystallization accompanying host densification in all the nanocomposites with orthorhombic (T-phase) or monoclinic (M-phase) Nb
2O
5 nanocrystals dispersed in the amorphous SiO
2 phase, depending on the niobium content and annealing temperature. A high-intensity broadband emission in the near-infrared region assigned to the
4I
13/2 →
4I
15/2 transition of the Er
3+ ions was registered for all the nanocomposites. The shape and the bandwidth changed with the Nb
2O
5 crystalline phase, with values achieving up to 81 nm. Er
3+ ions were located mainly in Nb
2O
5-rich regions, and the complex structure of the different Nb
2O
5 polymorphs accounted for the broadening in the emission spectra. The materials containing the T-phase, displayed higher luminescence intensity, longer
4I
13/2 lifetime and broader bandwidth. In conclusion, these nanostructured materials are potential candidates for photonic applications like optical amplifiers and WDM devices operating in the S, C, and L telecommunication bands.
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