The structural role of titanium in Ca–Sr–Zn–Si/Ti glasses for medical applications

Glasses for medical applications are used in particulate form or as a cement component. This work was undertaken to determine structural changes in 0.48SiO2–0.36ZnO–0.12CaO–0.04SrO glass when the SiO2 is substituted with 5 mol% increments of TiO2. X-ray Diffraction (XRD) was used to determine the presence of crystallinity. This occurred after additions of 20 mol% TiO2. Differential Thermal Analysis (DTA) and Network connectivity (NC) calculations determined that by increasing the TiO2 content, the Tg and NC reduced (Tg 670 °C to 632 °C, NC 1.83 to −1.14) suggesting that TiO2 acts as a modifying oxide. X-ray Photoelectron Spectroscopy (XPS) was used to determine the glass composition and the relative fraction of Bridging Oxygens (BO) to Non-Bridging Oxygens (NBO). XPS revealed that by increasing the concentration of TiO2, the NBO concentration increases, further suggesting the modifying role of Ti. The NBO/BO ratio was found to increase from 1.2 to 9.0 as the TiO2 content increased from 0 to 20 mol% additions. Raman spectroscopy was used to determine the Q-Structure of the glass series and found that the addition of TiO2 reduced the Raman shift from containing predominantly Q1/Q2 units when no Ti was present to Q0/Q1 with TiO2 additions.