Structure and properties of phosphate glasses prepared from lead and cadmium

A study of the structure and properties of phosphate glasses prepared from batches composed of ammonium dihydrogenphosphate (NH4)(RPO4)-P-2, lead chlo ride (PbCl2) and cadmium chloride (CdCl2) is described. The aim of this ela boration process is both chloride elimination and heavy metal incorporation into the phosphate matrix during batch reactions. Chemical analyses show t hat glasses containing less than 40 mol% P2O5 retain a significant amount o f residual chlorides. phosphate network depolymerisation is clearly shown c is P2O5 content in the glass decreases, using P-31 MAS-NMR. There is no evi dence for P-Cl bonds on P-31 MAS-NMR spectra. Evolution of lead local envir onment deduced from Pb-207 NMR shows that lead cations are involved into mo re covalent bonding as the amount of P2O5 in the glass decreases. There is no distinct contribution for lead chloride on Pb-207 NMR spectra. The evolu tion of glass transition temperature and chemical durability, with glass co mposition is in accordance with the presence of chlorides trapped into the glass network.