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The influence of strontium substitution in fluorapatite glasses and glass-ceramics |
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| Authors: | RG Hill A Stamboulis A Clifford C Crowley |
| Institution: | a Department of Materials, Imperial College London, South Kensington Campus, London SW7 2AZ, UK b Department of Chemistry, Imperial College London, South Kensington Campus, London SW7 2AZ, UK c Department of Materials, University of Limerick, Plassey, Limerick, Ireland d Materials Ireland Research Centre, Plassey Park, Limerick, Ireland |
| Abstract: | Strontium is often substituted for calcium in order to confer radio-opacity in glasses used for dental cements, biocomposites and bioglass-ceramics. The present paper investigates the influence of substituting strontium for calcium in a glass of the following composition: 4.5SiO23Al2O31.5P2O53CaO2CaF2, having a Ca:P ratio of 1.67 corresponding to calcium fluorapatite (Ca5(PO4)3F). The glasses were characterized by magic angle spinning nuclear magnetic resonance (MAS-NMR), by differential scanning calorimetry (DSC) and X-ray powder diffraction (XRD). The 29Si, 27Al and 31P NMR spectra for the glasses with different strontium contents were identical. The 19F spectra indicated the presence of F-Ca(n) and Al-F-Ca(n) species in the calcium glasses and in the strontium glasses F-Sr(n) and Al-F-Sr(n). It can be concluded that strontium substitutes for calcium with little change in the glass structure as a result of their similar charge to size ratio. The low strontium glasses bulk nucleated to a calcium apatite phase. Intermediate strontium content glasses surface nucleated to a mixed calcium-strontium apatite and the fully strontium substituted glass to strontium fluorapatite. |
| Keywords: | C290 N240 F170 |
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