Oxygen Non-Stoichiometry and Electrical Conductivity of LA0.2Sr0.8Fe0.8B0.2O3-d, B = Fe, Ti, Ta

O.F. Lohne, T.N. Phung, T. Grande, Henricus J.M. Bouwmeester, P.V. Hendriksen, M. Sogaard, K. Wiik

Research output: Contribution to journalArticleAcademicpeer-review

7 Citations (Scopus)

Abstract

The oxygen non-stoichiometry was determined by coulometric titration for the perovskite oxides La0.2Sr0.8FeO3−δ and La0.2Sr0.8Fe0.8B0.2O3−δ (B = Ti4+ and Ta5+) in the temperature range 600 ◦C ≤ T ≤ 900 ◦C and the oxygen partial pressure range: 1 · 10−15 ≤ pO2 ≤ 0.209 atm. The non-stoichiometry (δ) is observed to decrease with B-site substitution of Fe. The data can be well fitted with simple defect chemistry models. At low oxygen non-stoichiometry all compositions show a deviation from a localized electrons defect model. The standard and partial molar thermodynamic quantities were obtained and a gradual transition from localized to itinerant electrons with decreasing non-stoichiometry is proposed from the δ-dependency of the configurational entropy. The absolute value of the enthalpy of oxidation decreases upon B-site substitution of Fe proposing a decreased thermodynamic stability for the substituted materials. The electrical conductivity was measured at T = 900 ◦C in the oxygen partial pressure range: 1 · 10−17 ≤ pO2 ≤ 0.209 atm. The electrical conductivity and charge carrier mobility decrease upon 20% substitution of Fe roughly by a factor of 2, but do not show a significant dependence on the nature of the B-site dopant.
Original languageEnglish
Pages (from-to)F176-F184
JournalJournal of the Electrochemical Society
Volume161
Issue number3
DOIs
Publication statusPublished - 2014

Keywords

  • IR-89139
  • METIS-302024

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