THE SHORT-RANGE STRUCTURE OF ZINC POLYPHOSPHATE GLASS

P-31 magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy and Raman spectroscopy have been used to examine the polyhedral arrangements in xZnO . (1 - x)P2O5 (0.50 less than or equal to x less than or equal to 0.71) glasses. The depolymerization of P metaphosphate chains by the addition of ZnO is quantitatively described by the increase in the concentration of Q(1)-phosphate sites, determined from the P-31 MAS-NMR spectra. When x > 0.60, the NMR and Raman spectra exhibit peaks due to Q(0) and Q(2) tetrahedra, indicating that structures disproportionate in glass melts near the pyrophosphate composition. The splitting of the Raman peak due to the Q(1) terminal oxygen stretching mode indicates that a variety of P-O-Zn bonds participate in the polyphosphate glass structure. The complex mixture of P and Zn polyhedra contributes to the glass-forming tendency of the high ZnO (> 60 mol%) compositions.