Composition-dependent loss of phosphorus in the formation of transition-metal phosphate glasses

Phosphate glasses containing MnO₂, Co₃O₄ and CuO analyzed by Rutherford backscattering spectroscopy (RBS) have higher transition-metal (TM) concentrations in the glass than the initial batch composition. These compositional changes result from vaporization of phosphorus during the melt and are greater for the lower TM oxide batch composition glasses. X-ray photoelectron spectroscopy (XPS) shows that the copper ions exist as Cu⁺ and Cu²⁺, while cobalt ions exist as high-spin Co²⁺. The oxidation states for the Mn phosphate glasses could not be determined by XPS. The magnetization results, combined with RBS, indicate that more than 90% of the Cu ions occur as Cu²⁺, that all Co ions are in the high-spin Co²⁺ state and that more than half the manganese ions exist in the Mn²⁺ state. In addition to the measured phosphorus-to-metal atomic ratios, R, for the glasses being much less than those for the initial batch compositions, the R(glass) are essentially constant for R(batch) greater than ~∼ 2.5, independent of the TM ion and the initial batch composition. This suggests that phosphate glasses containing relatively small quantities of cations probably exist as ultraphosphate networks.