Mixed Network Phosphate Glasses: Seeing Beyond the 1D 31P MAS-NMR Spectra With 2D X/31P NMR Correlation Maps

Abstract

Abstract Much attention has been devoted to mixed network phosphate glasses during the last decades. Compared to simple network phosphate glasses, this type of glass presents interesting properties and improved stability deriving from the synergic association between P2O5 and another glass network former oxide. While solid state NMR appears to be the technique of choice to investigate both local and medium range structures of these materials, standard 1D 31P MAS-NMR spectra appear to be composed of very broad and uninformative signals coming from the superimposition of several resonances with close chemical shift values. The 1D NMR experiments do not provide interesting information and, as a consequence, the derived structural characterisation is limited and does not allow for a deep understanding of the macroscopic properties of these materials. In this review, we will present how the editing of 2D 31P/X correlation maps can overcome the poor resolution of the 1D 31P NMR analysis to provide detailed structural data. Through different examples, we will show how the 2D maps can be used to better understand the complex structure of these glasses and to help in the 1D 31P MAS-NMR analysis by (i) numbering the number of phosphate species, (ii) distinguishing P atoms involved in P–O–P and P–O–X bonds, and (iii) extracting NMR parameters (δCS, broadness) that will be used as input data for a supported and efficient 1D 31P NMR spectrum decomposition.