Understanding the anomalous behavior of Vegard's law in Ce1−xMxO2 (M = Sn and Ti; 0 < x ≤ 0.5) solid solutions. Issue 20 (6th May 2016)

• Record Type: Journal Article
• Authors: Baidya, Tinku; Bera, Parthasarathi; Kröcher, Oliver; Safonova, Olga; Abdala, Paula M.; Gerke, Birgit; Pöttgen, Rainer; Priolkar, Kaustubh R.; Mandal, Tapas Kumar
• Is Part Of: Physical chemistry chemical physics. Volume 18:Issue 20(2016)
• Page Start: 13974
• Page End: 13983
• Publication Date: 2016-05-06
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c6cp01525e
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : A lattice parameter vs. &#39; x &#39; curve in Ce1− x Sn x O2 ( x = 0.0–0.5) solid solutions is deviated from systematic linearity unlike in Ce1− x Zr x O2 due to higher electronegativity of Sn. Abstract : The dependence of the lattice parameter on dopant concentration in Ce1− x M x O2 (M = Sn and Ti) solid solutions is not linear. A change towards a steeper slope is observed around x ∼ 0.35, though the fluorite structure (space group Fm 3 m ) is preserved up to x = 0.5. This phenomenon has not been observed for Ce1− x Zr x O2 solid solutions showing a perfectly linear decrease of the lattice parameter up to x = 0.5. In order to understand this behavior, the oxidation state of the metal ions, the disorder in the oxygen substructure and the nature of metal–oxygen bonds have been analyzed by XPS, 119 Sn Mössbauer spectroscopy and X-ray absorption spectroscopy. It is observed that the first Sn–O coordination shell in Ce1− x Sn x O2 is more compact and less flexible than that of Ce–O. The Sn coordination remains symmetric with eight equivalent, shorter Sn–O bonds, while Ce–O coordination gradually splits into a range of eight non-equivalent bonds compensating for the difference in the ionic radii of Ce 4+ and Sn 4+ . Thus, a long-range effect of Sn doping is hardly extended throughout the lattice in Ce1− x Sn x O2 . In contrast, for Ce1− x Zr x O2 solid solutions, both Ce and Zr have similar local coordination creating similar rearrangement of the oxygen substructure and showing a linear lattice parameter decrease up to 50% Zr substitution. We suggest that the localized effect of Sn substitution due to its higher electronegativity may be responsible for the deviation from Vegard&#39;s law in Ce1− x Sn x O2 solid solutions.