Effect of Niobium Oxide on the Structure and Properties of Melt-Derived Bioactive Glasses

The effects of adding Nb2O5 on the physical properties and glass structure of two glass series derived from the 45S5 Bioglass® have been studied. The multinuclear 29Si, 31P, and 23Na solid‐state MAS NMR spectra of the glasses, Raman spectroscopy and the determination of some physical properties have generated insight into the structure of the glasses. The 29Si MAS NMR spectra suggest that Nb5+ ions create cross‐links between several oxygen sites, breaking Si–O–Si bonds to form a range of polyhedra [Nb(OM)6−y(OSi)y], where 1 ≤ y ≤ 5 and M = Na, Ca, or P. The Raman spectra show that the Nb–O–P bonds would occur in the terminal sites. Adding Nb2O5 significantly increases the density and the stability against devitrification, as indicated by ΔT(Tx − Tg). Bioglass particle dispersions prepared by incorporating up to 1.3 mol% Nb2O5 by replacing P2O5 or up to 1.0 mol% Nb2O5 by replacing SiO2 in 45S5 Bioglass® using deionized water or solutions buffered with HEPES showed a significant increase in the pH during the early steps of the reaction, compared using the rate and magnitude during the earliest stages of BG45S5 dissolution.