Journal
SOLID STATE IONICS
Volume 229, Issue -, Pages 26-32Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.ssi.2012.10.004
Keywords
Proton conductivity; Disorder; Pyrochlores; Fluorites; Isotope effect; TG-DSC
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Funding
- European Union, FP7 EFFIPRO project: Efficient and robust fuel cell with novel ceramic proton conducting electrolyte [227560]
- Danish Council for Strategic Research [09-064274]
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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)(2)O7-delta (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 degrees 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. (c) 2012 Elsevier B.V. All rights reserved.
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