ABSTRACT The optical properties of glass are strongly influenced by the redox states of trace multivalent elements. Ce 4 + ions are commonly added to soda‐lime glass to remove Fe 2 + ‐induced coloration via the redox reaction Ce 4 + + Fe 2 + → Ce 3 + + Fe 3 + during cooling. Herein, the redox dynamics of cerium ions in soda‐lime glass melts during model industrial cooling processes (from 1523 K at 20 K∙min −1 ) were investigated using in situ time‐resolved Ce K‐edge dispersive X‐ray absorption fine‐structure (DXAFS) spectroscopy. To evaluate the effect of the iron concentration, three soda‐lime glass samples containing 2 mass% CeO 2 were examined: Fe‐free, Fe‐05 (0.5 mass% Fe 2 O 3 ), and Fe‐20 (2.0 mass% Fe 2 O 3 ). Above 1383 K, the Ce 3 + /total Ce ratio remained stable for all samples, showing no significant change during cooling. Below 1383 K, the ratio decreased for the Fe‐free glass, indicating the oxidation of Ce 3 + ions, and increased for the Fe‐containing glass owing to the reduction of Ce 4 + ions. The temperature dependence of the redox change ( Δ Ce redox) showed Fe‐dependent behavior: Fe‐20 exhibited more pronounced Ce 4+ reduction above 1200 K, while Fe‐05 showed accelerated changes mainly below approximately 1100 K. These results indicate that cerium oxidation in Fe‐free glass is strongly influenced by oxygen transport limitations, while cerium reduction is closely associated with availability of Fe 2 + ions, providing quantitative insights into the control of Ce‐based decolorization during industrial cooling.
Ozawa et al. (2026) studied this question.