INTERMEDIATE-RANGE ORDER IN SIMPLE METAL-PHOSPHATE GLASSES - THE EFFECT OF METAL-CATIONS ON THE PHOSPHATE-ANION DISTRIBUTION

The technique of high-performance liquid chromatography (HPLC) has bee n used to determine the phosphate-anion distribution in a variety of m etal phosphate glasses-including glasses made with the trivalent metal cations: Al, In, Ga, and La. The composition of each glass was chosen so that the average phosphate chain length was between 2 and 4 PO4 te trahedra. The widths of the resulting phosphate-anion chain-length dis tributions were determined directly from an analysis of the HPLC chrom atograms. Literature values for the free energy of formation of the cr ystalline metal-orthophosphate compounds with respect to P2O5 and the metal oxide were compared to the width of the phosphate-anion chain-le ngth distributions. We found that the smaller the energy of formation, the wider the distribution of phosphate chains, and the greater the e ase of glass formation. (C) 1998 Published by Elsevier Science B.V. Al l rights reserved.