NA-23 CHEMICAL-SHIFTS AND LOCAL-STRUCTURE IN CRYSTALLINE, GLASSY, ANDMOLTEN SODIUM BORATES AND GERMANATES

A simple correlation between average Na-O bond length and Na-23 isotro pic chemical shift in crystalline germanates and berates has been esta blished, similar to existing correlations for sodium in silicates and carbonates. This empirical trend is discussed in terms of a decreasing paramagnetic contribution to the chemical shift with increasing avera ge bond length. The correlation is then applied to data for sodium ber ate and germanate glasses and melts from room temperature to 1200 degr ees C, where both structural and compositional effects on the chemical shift are apparent. (C) 1997 Elsevier Science B.V.