The Effects of Silicon Oxide on the Structure, Physical Chemistry Properties, and Bioactivity of Phosphate Glasses Containing Sodium, Strontium, and Titanium Oxides

Glasses with molar compositions 40Na2O-10SrO-(20-x)TiO2-xSiO2-30P2O5 (0 ≤ x ≤ 10; O/P = 4), were prepared by the classical melt-quenching technique and structurally characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), Raman, nuclear magnetic resonance (NMR), and density measurements. The introduction of SiO2 into the phosphate glass slightly weakened the glass network, as shown by the small increase in the molar volume (VM) and the decrease in the glass transition temperature (Tg). This behavior was due to the existence of more ionic P-O-Si than P-O-P bonds. Spectroscopic studies showed that SiO2, like P2O5 oxide, behaved as a network former and that the glass structure contained P-O, P-O-P, Si-O, Si-O-Si, Ti-O, Ti-O-Ti, P-O-Ti, and P-O-Si linkages. The preliminary results of the in vitro bioactivity tests showed the existence of ionic exchanges between the simulated body fluid (SBF) solution and the studied glasses. X-ray powder diffraction and FTIR spectroscopy confirmed the formation of the Ca-P layer on the surfaces of the tested compositions.