Sol-gel synthesis and structural characterization of P2O5-CaO-Na2O glasses

Ternary phosphate-based glasses in the system P2O5-CaO-Na2O have been successfully synthesized using a new low temperature sol-gel method. The glasses have a fixed P2O5 content of 45 or 50 mol% and the CaO:Na2O ratio was varied The synthesized systems which remained fully amorphous have been characterized using x-ray diffraction (XRD) and their thermal properties have been examined by differential thermal analysis (DTA). The structure of the phosphate network has been studied as a function of composition using Fourier transform infrared (FTIR) spectroscopy and P-31 nuclear magnetic resonance (NMR). The XRD results reveal that none of the glasses contain any crystalline phases, while the DTA results reveal increases in the glass transition, crystallization and melting temperatures with decreasing Na2O content. The FTIR and P-31 NMR results show that the dried gel has a structure dominated by Q(0), Q(1) and relatively small amounts of Q(2) groups, whereas that of the stabilized sol-gel derived glass is composed of mainly Q(1) and Q(2) species. These results provide several interesting insights into phosphate sol-gel chemistry and indicate their suitability for further study with a view to developing biomedical applications of these glasses in the future.