NMR-STUDIES OF PHOSPHORUS IN SI-P-TE AND GE-P-TE GLASSES

Glass formation and structure in the systems P-Ge-Te and P-Si-Te has b een studied by nuclear magnetic resonance (NMR) including P-31 magic-a ngle spinning, spin echo decay spectroscopy, and in situ molten-state investigations. Despite similar regions of glass formation, NMR result s illustrate dramatic structural differences between the two systems. In P-Ge-Te glasses homopolar P-P bonding appears to be predominant, wh ile the P-Si-Te glass system shows a much greater tendency towards het eropolar bonding, qualitatively consistent with a randomized chemical bonding. Constraints posed by these NMR experiments upon possible mode ls of glass structure are discussed. (C) 1997 Elsevier Science B.V.