Structural study of phosphorus oxynitride glasses LiNaPbPON by nuclear magnetic resonance and X-ray photoelectron spectroscopy

The structure of Li _0.25Na _0.25Pb _0.25PO _3−3x/2N _x (0< x ⩽0.69) nitrided glasses has been studied by nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS). ³¹ P magic angle spinning (MAS) NMR shows that the glass network is built up of PO ₄, PO ₃N and PO ₂N ₂ tetrahedral units. PO ₄–PO ₄, PO ₄–PO ₃N and PO ₃N–PO ₂N ₂ connections, characterized with double quantum (DQ) ³¹P MAS NMR, are homogeneously distributed within the glass network. XPS at the N _1s core level indicates that nitrogen atoms substitute for bridging (–O–) and terminal (O) oxygen atoms, as two-coordinated –N = (N _d) or three-coordinated –N < (N _t) species. A higher amount of N _d than N _t species is found for the highest nitrogen contents. ²³Na and ²⁰⁷Pb NMR results show that the oxygen atoms coordinating modifier cations are not concerned by the nitrogen–oxygen substitution. The role played by lead in these ‘LiNaPbPON’ glasses can be deduced from a comparison with similar ‘LiNaPON’ glasses. The presence of Pb ²⁺ ions clearly affects the nitridation mechanism and their network former character increases with nitridation.