Effect of CaO on the structure, durability and bioactivity properties of phosphate Na2O–SrO–TiO2–P2O5 glasses

Abstract

This study aims to investigate the influence of calcium oxide on the structure, thermal, durability, and bioactivity properties of new phosphate glasses within the (40-x) Na2O-xCaO-10SrO-20TiO2-30P2O5 system (0 ≤ x ≤ 30). Glass samples have been prepared by the classical method of melting followed by quenching and characterized by XRD, DTA and IR. The introduction of the CaO oxide instead of Na2O in the glasses strengthens the vitreous network, as shown by the increase of the glass transition temperature and the decrease of the molar volume and the dissolution rate. This behavior is a result of the replacement of Na-O bonds by more covalent Ca-O bonds. FTIR spectroscopy study shows that the glasses structure consists of PO4, P2O7 groups, and TiO6 octahedra, with -O-Ti-O-P-O- linkages. Powder X-ray diffraction reveals that crystallization of the glasses leads to the formation of a mixture of phases. The reactivity of these glasses in the SBF solution was followed by XRD and by FTIR spectroscopy. The obtained results of the in vitro bioactivity tests reveal the ability of the studied glasses to form hydroxyapatite layers on their surfaces after immersion in SBF solution.