Structure of oxynitride phosphate glasses in the system Li-Na-Pb-P-O-N

The structure of Li 0.25 Na 0.25 Pb 0.25 PO 3-3x/2 N x glasses has been studied by Raman, Nuclear Magnetic Resonance and X-ray Photoelectron Spectroscopies. 31 P MAS NMR shows that the glass network is built up of PO 4 , PO 3 N and PO 2 N 2 tetrahedral units. PO 4 -PO 4 , PO 4 -PO 3 N and PO 3 N-PO 2 N 2 correlations, characterized with 31 P DQ MAS NMR, are homogeneously distributed within the glass network. XPS at the N 1s core level indicates that nitrogen atoms substitute for bridging and non-bridging oxygen atoms, as two-coordinated, -N= (N d ), or three-coordinated, -N< (N t ), nitrogen species. The role played by lead in these glasses is derived from a comparison with the nitridation process in LiNaPON and NaPON glasses. The presence of Pb 2+ ions clearly affects the nitridation mechanism while their network former character increases with nitridation.