Correlation of the oxidation state of cerium in sol-gel glasses as a function of thermal treatment via optical spectroscopy and XANES studies

Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Zerihun AssefaD K Shuh

Abstract

Sol-gel glass matrices containing lanthanides have numerous technological applications and their formation involves several chemical facets. In the case of cerium, its ability to exist in two different oxidation states or in mixed valence state provides additional complexities for the sol-gel process. The oxidation state of cerium present during different facets of preparation of sol-gel glasses, and also as a function of the starting oxidation state of cerium added, were studied both by optical spectroscopy and X-ray absorption near-edge structures (XANES). The findings acquired by each approach were compared. The primary focus was on the redox chemistries associated with sample preparation, gelation, and thermal treatment. When Ce3+ is introduced into the starting sols, the trivalent state normally prevails in the wet and room temperature-dried gels. Heating in air at >100 degrees C can generate a light yellow coloration with partial oxidation to the tetravalent state. Above 200 degrees C and up to approximately 1000 degrees C, cerium is oxidized to its tetravalent state. In contrast, when tetravalent cerium is introduced into the sol, both the wet and room temperature-dried gels lose the yellow-brown color of the initial cer...Continue Reading

Citations

Aug 5, 2009·Chemical Reviews·Koen Binnemans
Feb 25, 2015·The Journal of Physical Chemistry. B·Valentina NicoliniSergio Valeri
Sep 2, 2021·ACS Biomaterials Science & Engineering·Alfonso ZambonGigliola Lusvardi

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