Structural and thermal influence of niobia in aluminoborosilicate glasses

The addition of small amounts of niobia (Nb₂O₅) in borosilicate glasses was explored. By analysis on thermal and structural changes, we found evidences that niobium integrates the glass structure in octahedral NbO₆ coordination. Adding up to 8.0 mol% of Nb₂O₅, the oxide partially ruptured the glass structure, interfering in the BO₃/BO₄ ratio, but the predominant network configuration was maintained. Thermally, there was an increase in the processing interval and the glasses became more resistant against crystallization, with the presence of niobia. Also, the oxide contributed to a notable decrease in the viscosity of the melts. The improvement of such properties were obtained by the controlled dispersion of the oxide in the glass network structure, avoiding large areas of phase-to-phase separation to preserve the desired ability of these glasses to incorporate a wide range of elements.