A structural study of sol–gel and melt-quenched phosphate-based glasses Daniela Carta a , David M. Pickup a , Jonathan C. Knowles b , I. Ahmed b , Mark E. Smith c , Robert J. Newport a, * a School of Physical Sciences, Ingram Building, University of Kent, Canterbury CT2 7NH, UK b Division of Biomaterials and Tissue Engineering, UCL Eastman Dental Institute, 256 Gray’s Inn Road, London WC1X 8LD, UK c Department of Physics, University of Warwick, Coventry CV4 7AL, UK Available online 27 March 2007 Abstract Phosphate-based glasses have recently attracted much interest as a new generation of biomaterials because of their ability to react and dissolve in the physiological environment and eventually to be replaced by regenerated hard or soft tissue. A series of phosphate-based glasses containing 45 mol% P 2 O 5 and various amounts of CaO and Na 2 O were synthesized by sol–gel and melt-quenching techniques. A comparison between the structure of the sol–gel glass and the structure of the analogous melt-quenched glasses has been undertaken. A broad-based characterization approach combining different techniques has been used to investigate the short-range structure of the glasses and the effect of adding modifier oxides to the network structure (conventional and high energy X-ray diffraction, infra-red spec- troscopy, 31 P solid state magic angle spinning NMR spectroscopy). Sol–gel and melt-quenched glasses appear to have a similar structure, showing similar Q n distributions and atomic correlations. Ó 2007 Elsevier B.V. All rights reserved. PACS: 81.20.Fw; 81.05.Kf Keywords: Biomaterials; Phosphates; Sol–gels (xerogels) 1. Introduction The majority of glasses and glass ceramics used as bio- materials have hitherto been based on a silicate network, and they are mainly used as long-term implants as they are only slowly soluble in human body fluid. The novelty of the phosphate-based glasses studied in the present work is related to their unusually slow solubility in the human body fluid for phosphates. This makes them ideal materials for temporary implants as they are slowly replaced by the natural tissue as they dissolve in the body (and for this rea- son they are classified as bioresorbable). They can also be used as drug delivery systems (antibiotics, biological active agents) as they can deliver drugs within the body in a con- trolled way. Recently, melt-quenched ternary bioresorable glasses in the system P 2 O 5 –CaO–Na 2 O, with P 2 O 5 in the range 40–55 mol% and CaO 8–40 mol%, have been developed [1–4]. In particular, compositions based on 45 mol% P 2 O 5 , with CaO in the range 20–40 mol% and Na 2 O in the range 35–15 mol%, are particularly interesting because in vitro studies, performed by incubating human osteoblast cell lines on these glasses, show a good biological response [5]. The modifier oxides CaO and Na 2 O are added to the phosphate network in order to tailor the glass solubility to the specific in vivo situations. However, the melt-quench- ing technique has some disadvantages: the high tempera- tures (1000 °C) required for this synthetic route can cause high loss of the volatile phosphorus precursor during the synthesis; furthermore, bioactive molecules such as 0022-3093/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2007.02.008 * Corresponding author. E-mail address: r.j.newport@kent.ac.uk (R.J. Newport). www.elsevier.com/locate/jnoncrysol Journal of Non-Crystalline Solids 353 (2007) 1759–1765