Investigation of the solubility and ion release in the glass system K2O-Na2O-CaO-P2O5

Glasses from the quaternary glass system K2O-Na2O-CaO-P2O5 were produced by standard glass forming techniques. The compositions were limited by fixing the P2O5 at 45mol%, fixing the CaO content at either 20,24 or 28 mol%. The K2O and Na2O made up the residual varying from 0 to 25 mol % K2O. General trends showed that with increasing CaO content, the glasses showed a decrea se in solubility as expected. For a single system of fixed CaO content, wit h increasing K2O content, there was an increase in solubility. This was see n at all three CaO contents. All the glasses showed an initial increase in pH followed by a gradual decrease with time and this was accounted for by t he initial release of Na+ ions into solution. For the ion release curves, f or all fixed CaO contents, the glass with 0mol% K2O showed the lowest Ca2release. This was accounted for as being due to the low solubility compared to the K2O containing glasses. The Na+ release appeared anomalous, as it w as higher than all the K2O containing glasses. Even though the glasses with 0 mol% K2O showed the lowest solubility, the amount of Na+ contained in th e glass was high, hence the high levels of release. (C) 2001 Elsevier Scien ce Ltd. All rights reserved.