TiK-edge XANES study of the local environment of titanium in bioresorbable TiO2-CaO-Na2O-P2O5 glasses

Ti K-edge XANES (X-ray absorption near edge structure) spectroscopy has been used to study the local coordination of titanium in biocompatible and bioresorbable TiO2-CaO-Na2O-P2O5 glasses. Both conventional melt-quenched glasses of composition (TiO2) (x)(CaO)(0.30)(Na2O)((0.20-x))(P2O5)(0.50), where x = 0.01, 0.03 and 0.05, and sol-gel derived (TiO2)(0.25)(CaO)(0.25)(P2O5)(0.50) glass have been studied. The results show that in all the materials studied, titanium is surrounded by an octahedron of oxygen atoms. Further analysis reveals that the TiO6 site in the amorphous samples is not heavily distorted relative to that in rutile, anatase or CaSiTiO5. The spectra from the (TiO2)(0.25)(CaO)(0.25)(P2O5)(0.50) sol-gel samples reveal greater distortion in the TiO6 site in the dried gel compared to the heat-treated sol-gel glass. The XANES spectra from melt-quenched glass samples soaked in distilled water for various times do not shown any evidence of degradation of the titanium site over periods of up to 14 days.