NMR and Mössbauer characterization of tin(II)–tin(IV)–sodium phosphate glasses

xSnO–(100 − x)NaPO3 glasses were prepared under argon atmosphere for 0 ⩽ x ⩽ 40. Wet chemical analyses and Mössbauer spectroscopy indicate the presence of Sn(II) and Sn(IV) in the glasses, with a majority of Sn(II). 119Sn NMR and Mössbauer spectra show that the local environment of Sn(II) are characteristic of SnO in network forming sites. The 119Sn NMR spectrum of an oxidized glass shows that Sn(IV) are located in sites similar to SnP2O7. 31P MAS–NMR spectra show that the sodium metaphosphate chains are depolymerized by SnO, and that dissociation into the phosphate melt is complete. The 31P resonances were assigned to middle-chain group charge compensated by Na+(Q2(Na)), chain-end group charge compensated by Sn2+(Q1(Sn(II))) and Na+(Q1(Na)). The 31P MAS–NMR spectrum of the oxidized glass enabled to measure the chemical shift of (Q1(Sn(IV))), and the double-quantum filtered 31P MAS–NMR spectrum showed that Sn(IV) sites are inserted in the phosphate glass network.