In this study, a bioactive glass of eutectic composition based on Ca(PO)-CaSiO system was prepared and investigated. It was found that by controlling the nucleation and growth of crystals, a glass-ceramics free from cracks, containing one or two crystalline phases, and of controlled nano- to microscale microstructure can be obtained. Heat treatment of the parent glass produces various calcium phosphates (Ca-deficient apatite and α-tricalcium phosphate) and calcium silicates (pseudo-wollastonite and/or wollastonite-2M) plus amorphous phases. By combining a number of experimental techniques like P and Si magic angle spinning nuclear magnetic resonance spectroscopy, scanning and transmission electron microscopy, energy-dispersive X-ray spectrometry, and Rietveld analysis of X-ray diffraction patterns, a crystallization model was derived, capable of explaining the observed structural and microstructural changes. The determination of amorphous or crystalline phases enabled to produce time-temperature-transformation plots. The structural role on the behavior of these materials and its impact on their in vitro bioactivity are also discussed.

The authors acknowledge support of the E.U. COST Action MP 1301 Newgen (http://www.cost-newgen.org/).