A mas NMR investigation of lead phosphosilicate glasses: The nature of the highly deshielded six-coordinated silicon

29Si and 31P NMR spectra have been studied in a series of lead phosphosilicate glasses. It is found that as the P2O5 content increases, the signal due to the six-coordinated silicon at − 212 ppm grows in intensity. Based on partial charge arguments it is suggested that the six-coordinated silicon atoms are surrounded by only phosphorus as second neighbours and are highly desheilded.