QUANTITATIVE-DETERMINATION OF THE STRUCTURAL UNITS IN PHOSPHORUS-SELENIUM GLASSES BY P-31 DIPOLAR AND MAGIC-ANGLE-SPINNING NMR-SPECTROSCOPY

The detailed quantitative speciation of phosphorus and selenium microstructures in phosphorus-selenium glasses is derived from combined P-31 spin-echo and magic-angle-spinning NMR experiments. The results illustrate that the structure of these glasses differs from the chemically ordered or clustered structures previously proposed, but are also at variance with a completely random distribution. There is a distinct preference for the formation of P-Se versus P-P and Se-Se bonds, which can be quantified from the present experiments. The site speciation shows no dramatic changes near the composition (40 at. % P) corresponding to the rigidity percolation threshold.