Defect chemistry of singly and doubly doped ceria: Correlation between ion transport and energetics

Salih Buyukkilic, Sangtae Kim, Alexandra Navrotsky

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Earlier studies have shown a strong correlation between the enthalpy of formation, ΔHf,ox, and the ionic conductivity, σi, near room temperature in doped ceria systems, which are promising solid electrolytes for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The present work demonstrates that this correlation holds at the operating temperature of IT-SOFCs, 600-700-°C. Solid solutions of Ce 1-xNdxO2-0.5x, Ce1-xSm xO2-0.5x, and Ce1-xSm0.5xNd 0.5xO2-0.5x are studied. The ΔHf,ox at 702-°C is determined by considering the excess heat content between 25 and 702-°C combined with the value of ΔHf,ox at 25-°C. Both σi and ΔHf,ox show maxima at x=0.15 and 0.20 for the singly and doubly doped ceria, respectively, suggesting that the number of mobile oxygen vacancies in these solid solutions reaches a maximum near those compositions. An increase in temperature results in a shift of the maximum in both ΔHf,ox and σi towards higher concentrations. This shift results from a gradual increase in dissociation of the defect associates. A unique correlation: The correlation between the energetics and the ionic conductivity, σi, of ceria that was singly or doubly doped with neodymia and samaria has now also been confirmed for high temperatures. The maximum formation enthalpy of the oxide solid solution, ΔHf,ox, coincides with the maximum σi at/near dopant fractions of 0.10, 0.15, and 0.20 in Ce1-xNdxO 2-0.5x, Ce1-xSmxO2-0.5x, and Ce 1-xSm0.5xNd0.5xO2-0.5x, respectively.

Original languageEnglish (US)
Pages (from-to)9517-9521
Number of pages5
JournalAngewandte Chemie - International Edition
Volume53
Issue number36
DOIs
StatePublished - 2014
Externally publishedYes

Keywords

  • ceria
  • doping
  • ionic conductivity
  • materials science
  • solid solutions

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

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