Effects of melting temperature on cerium oxidation state and crystallization on catalytic properties in cerium phosphate glasses

Abstract

The effect of the melting temperature on the cerium oxidation state and crystallization of cerium phosphate glasses with a molar composition 30CeO₂–70P₂O₅ was investigated. Ce³⁺ and Ce⁴⁺ ion concentration changes in the glass attributable to the melting temperature were investigated by X-ray photoelectron spectroscopy analysis. The crystallization kinetics of the glasses and the activation energy for crystallization were evaluated under non-isothermal conditions using differential thermal analysis (DTA) performed at different heating rates. Each DTA curve exhibited one exothermic peak associated with the crystallization of the glass. The crystalline phase was identified as CePO₄ via X-ray diffractometry analysis. The Kissinger and Marotta methods were used to calculate the local activation energies for the glass samples. The amount of precipitated CePO₄ with heating at 890 K increased as the melting temperature (or Ce³⁺) increased. The catalytic properties were studied by thermogravimetric analysis, which showed that a greater amount of precipitated CePO₄ led to poorer catalytic properties of the glass.