NMR-STUDY OF CRYSTALLIZATION IN MGO-CAO-SIO2-P2O5 GLASS-CERAMICS

Si-29 and P-31 magic-angle-spinning (MAS) nuclear magnetic resonance ( NMR) measurements were employed to investigate crystallization in MgO- CaO-SiO2-P2O5 bioglass-ceramics. The results suggest that wollastonite (beta-CaSiO3) is separated as a new crystalline phase, corresponding to the appearance of a sharp signal in the Si-29 MAS NMR spectra, whil e oxyapatite (Ca-10(PO4)(6)O) forms in the process of the order of the phosphorus-rich phases increasing as a whole, corresponding to the gr adual narrowing of P-31 MAS NMR spectra. ZnO can make the glass stable and difficult to crystallize at a low temperature, while at a high te mperature, ZnO can participate in the crystallization of beta-CaSiO3 a nd promote it. (C) 1998 Elsevier Science B.V. All rights reserved.