New sol–gel synthesis of a (CaO)0.3(Na2O)0.2(P2O5)0.5 bioresorbable glass and its structural characterisation

An improved sol–gel synthesis of (CaO)0.3(Na2O)0.2(P2O5)0.5 bioresorbable glass has been developed. The structures of both the dried gel and the stabilised sol–gel glass have been characterised using high-energy XRD, 31P MAS NMR and FT-IR spectroscopy. The structure of the analogous melt-quench prepared glass has also been studied for comparison. The results show that the dried gel has a structure consisting of mainly Q0 and Q1 phosphate units, whereas that of the stabilised sol–gel glass comprises predominantly Q1 and Q2 units. Furthermore, it is demonstrated that the structure of the sol–gel glass is similar to that of its melt-quenched counterpart except for the presence of hydroxyl groups which terminate the phosphate chains, reducing the connectivity of the network.