Effects of Melting Conditions on Cerium Oxidation State and Catalytic Properties of CeO₂-P₂O5 Glass Systems.

Abstract

As with any solvent, stabilizing a multivalent element at a given oxidation state in glass depends on the thermodynamic conditions. The effects of temperature on the oxidation-reduction equilibrium have been previously noted with higher temperatures being more conducive to reduced states. Herein, 30CeO₂-70P₂O5 binary system glasses were prepared. The melting temperature and time dependency on Ce4+ and Ce3+ ion concentrations were studied using X-ray photoelectron spectroscopy. Different melting conditions were investigated at temperatures ranging from 1300 °C to 1500 °C for 60 min, and at 1400 °C for durations ranging from 30 min to 90 min. The changes in the catalytic properties of the glasses as a function of Ce4+ and Ce3+ ion concentrations were confirmed based on the changes in the decomposition starting temperatures using thermogravimetric analysis. The main changes in the oxidation states according to melting conditions were discussed in terms of the catalytic properties of CeO₂-P₂O5 glass systems.