Local structure of cerium in aluminophosphate and silicophosphate glasses

The local structure of cerium in two systematic compositional series of glasses, nominally CeP₃O₉-AlP₃O₉ and CeP₃O₉-SiP₂O₇, was interrogated using X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) spectroscopy. XPS revealed that, for glasses melted in air, ≥yen;95% of cerium ions are Ce³⁺. This was independently confirmed using X-ray absorption near edge spectroscopy (XANES). Ce K-edge extended X-ray absorption fine structure (EXAFS) has been used to determine the local structure of Ce ³⁺. Near the metaphosphate composition, cerium was found to have an average cerium coordination number of ~7.0 and an average cerium-oxygen bond length of 2.41 Å. The average cerium coordination number and average cerium-oxygen bond distance were found to increase with decreasing cerium concentration in both compositional series. Rare-earth clustering is suggested based on numerical calculations for glasses containing ≥yen;14 and ≥yen;15 mol% Ce₂O₃ for the aluminophosphate and silicophosphate series, respectively.