THE SHORT-RANGE STRUCTURE OF SODIUM ULTRAPHOSPHATE GLASSES

Anhydrous sodium ultraphosphate glasses were prepared with Na,O contents between O and 50 mol% and were characterized by several structurally sensitive spectroscopic probes to determine the nature of the phosphate tetrahedra that constitute the short-range glass structure. Solid state P-31 magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy reveals that Na2O depolymerizes the branched (Q(3)) P-O network of P2O5 to form metaphosphate (Q(2)) sites, in quantitative agreement with Van Water's 'chemically simple' model. X-ray photoelectron spectroscopy reveals that the concomitant increase in non-bridging oxygen with increasing Na2O content is also in quantitative agreement with this structural model. Raman spectroscopic analyses of glasses with approximately 40 mol% Na2O suggest that some intermediate-range order, perhaps associated with strained rings, also exists within the glass network. Strained sites are eliminated when the solid glass is heated to melt temperatures.