Canasite, K2Na4Ca5Si12O30(OH,F)4. glass ceramics are particularly noted for high fracture toughnesses (5MPam1/2) and bend strengths (300MPa). Their high fluorine content also ensures good castability of the melt. They are therefore promising candidates for hard tissue augmentation. Stoichiometric compositions are however bioinert. Recently, the addition of a few mol% P2O5 to canasite has been shown to induce bioactivity in canasite. The effect of P2O5 on glass formation and crystallisation has been studied in two series of canasite based glasses. The first is a stoichiometric canasite series in which the F content only was varied. In the second series, the F content was varied in a similar way but the Na2O concentration was approximately half that present in the canasite formula unit. X-ray diffraction (XRD) and transmission electron microscopy (TEM) have been used to study phase evolution as a function of composition and temperature.
