ANALYSIS BY NUCLEAR-MAGNETIC-RESONANCE AND RAMAN SPECTROSCOPIES OF THE STRUCTURE OF BIOACTIVE ALKALINE-EARTH SILICOPHOSPHATE GLASSES

Structural knowledge of bioactive glass systems is necessary to unders tand their biological properties and improve their mechanical and clin ical performance. In this work, the local structure of P and Si in bio active glasses of the system CaO-SiO2-P2O5-CaF2 with different Mg or S r contents was determined, by means of P-31 and Si-29 magic-angle samp le-spinning nuclear magnetic resonance (MASS NMR) and Raman spectrosco pies. The results show that phosphorus is located in calcium-orthophos phate domains, surrounded by silicate species containing 1, 2 and 3 br idging-oxygens per SiO4 tetrahedra. The type and relative distribution of the silicate units do not depend on the nature of the alkaline ear th cations present in the system. However, the increase of RO content decreases the degree of polymerization of silicon tetrahedra, while PO 4 monomeric units remain unchanged. An interpretation of the medium-ra nge structure of the glass is suggested.