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 T_g and NC reduced (T_g 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.