Spectral editing based on scalar spin-spin interactions: new results on the structure of metathiophosphate glasses

The local structure of glassy NaPS(3) and AgPS(3) was analyzed based on quantitative (31)P MAS-NMR spectroscopy. The glasses contain some oxide impurities, which could be quantified from the NMR spectral analysis. Four discrete resonances are observed in both glasses, which were assigned to four distinct types of phosphate groups P((n)), where n is the number of P-S-P bridges(i.e., P((0)), P((1)), P((2)), and P((3)) units, respectively) with the help of 2D homonuclear J-resolved and INADEQUATE methods. Based on the results obtained, the interpretations of previous spectra obtained at low spinning speeds on lithium and silver thiophosphate glasses (Chem. Mater. 2 (1990), 273, and J. Am. Chem. Soc. 114 (1992), 5775) need to be revised. Contrary to the situation in alkali phosphate glasses, the corresponding sulfide analogs are characterized by a wide P((n)) species distribution close to that predicted by a statistical charge distribution. INADEQUATE experiments fail to detect P((n))-P((n-1)) connectivities, suggesting that the structure of these glasses is rather inhomogeneous, possibly featuring the different P((n)) species in segregated domains.