Effect of sodium doping in β-tricalcium phosphate on its structure and properties

For the preparation of beta-TCP and biphasic calcium phosphates (BCPs, mixtures of hydroxyapatite and beta-TCP), the presence of sodium in the reaction medium results in the incorporation of sodium in the beta-TCP network, by substitution of some calcium sites. Accordingly, a decrease of the unit cell volume of beta-TCP was observed with increasing sodium substitution. The distribution of sodium in the beta-TCP structure, as a function of the amount incorporated, was probed using IT and Na-23 MAS NMR and 31P{Na-23} REDOR experiments. It was shown that an estimation of the sodium content in beta-TCPs could be obtained from the modeling of their IT MAS NMR spectra. Moreover, the incorporation of sodium in beta-TCPs results in improved mechanical properties, without affecting the biocompatibility of the ceramics.