Comment on an article by Gonzaga et al. J Am Ceram Soc. 2020;103:6280‐6288

Abstract I argue that the authors’ interpretation of X‐ray photoelectron spectroscopy (XPS) Ce3d spectra of their materials is untenable because it largely neglects the electronic structure of cerium ions and spin‐orbit interaction of the Ce3d subshell. I conclude that at %Ce 3+ values the authors derived from their Ce3d spectra offer an inaccurate account of the cerium chemistry of their materials.