Sol-gel synthesis of the P2O5-CaO-Na 2O-SiO2 system as a novel bioresorbable glass

Abstract

A series of phosphate-based sol-gel glasses in the system P 2O5-CaO-Na2O-SiO2 were synthesised using PO(OH)3-x(OC2H5)x (x = 1, 2) as a phosphorus precursor and alkoxides of sodium, calcium and silicon in an ethylene glycol solution. It has been found that the upper limit for gel formation is about 22 mol% phosphorus and that the gelation time increases with increasing phosphorus content of the sol. X-ray diffraction (XRD) along with X-ray fluorescence chemical analysis (XRF) have been performed on samples containing 45 mol% of P2O5 and 0, 10, 15 and 25 mol% of SiO2 with varying amount of modifier oxides (CaO, Na2O). All the samples are predominantly amorphous up to 400 °C and some of them, depending on the composition, retain their amorphous structure up to 600 and 800 °C. To the knowledge of the authors, this is the first time that phosphate-based glasses having these compositions have successfully been synthesised via the sol-gel method. © The Royal Society of Chemistry 2005.