Conductivity and hydration trends in disordered fluorite and pyrochlore oxides: A study on lanthanum cerate–zirconate based compounds

Vasileios Besikiotis, Sandrine Ricote, Molly Hjorth Jensen, Truls Norby, Reidar Haugsrud

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

In the present contribution we discuss the influence of order/disorder on the concentration and mobility of ionic charge carriers in undoped and acceptor (calcium) doped fluorite and pyrochlore structured lanthanum cerate–zirconate solid solutions: (La1−yCay)2(Ce1−xZrx)2O7−δ (y=0, 0.02, 0.10; x=0, 0.50, 0.75). Characterization of the electrical conductivity as a function of temperature and oxygen partial pressure revealed contribution from electronic carriers in reducing atmosphere, but otherwise these materials are ionic conductors. Oxide ion conductivity dominates at high temperatures while protons become more dominating as charge carrier at temperatures below typically 500°C under wet conditions. The hydration enthalpies were determined by simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC). The contribution from ionic conductivity increases and the hydration enthalpy becomes more exothermic with higher cerium content, i.e. with more disordered materials. The proton conductivity decreases upon acceptor substitution of La3+ with Ca2+ which is attributed to trapping of the charge carriers by the effectively negative acceptor.
Original languageEnglish
JournalSolid State Ionics
Volume229
Pages (from-to)26-32
ISSN0167-2738
DOIs
Publication statusPublished - 2012

Keywords

  • Proton conductivity
  • Disorder
  • Pyrochlores
  • Fluorites
  • Isotope effect
  • TG-DSC

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