Effects of A- and B-site (co-)acceptor doping on the structure and proton conductivity of LaNbO4

Publication: Research - peer-reviewConference article – Annual report year: 2011

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B-site and A- and B-site co-doped lanthanum niobates, La(1-x)DA(x)Nb(1-y)DB(y)O(4-δ), where DA stands for Ca or Ba and DB for Ga, Ge or In (x = 0 or 0.01; y = 0.01), have been synthesized via the solid-state route. Essentially single-phase materials were obtained after 10 h at 1500 °C with monoclinic Fergusonite structure at room temperature. The unit cell volume increases slightly with the presence of the acceptor. The electrical conductivity of the materials, characterized as a function of the temperature from 300 °C to 900 °C under wet reducing conditions with AC impedance spectroscopy, was dominated by protons. The maximum conductivity of 4.1 · 10−4 S · cm−1 at 900 °C was obtained for La0.99Ca0.01Nb0.99Ga0.01O4-δ, which is a factor of ~ 2.5 lower than the highest conductivity reported for the A-site Ca-doped LaNbO4. Based on a semi-quantitative evaluation it was shown that the hydration of the B-site and A- and B-site co-doped LaNbO4 is slightly more exothermic and that the proton mobility has higher activation enthalpies than Ca-doped LaNbO4. This is accounted for by a stronger association between the acceptor and the proton for B-site than for A-site doping.
Original languageEnglish
JournalSolid State Ionics
Publication date2012
Volume213
Pages45-52
ISSN0167-2738
DOIs
StatePublished

Conference

Conference15th International Conference on Solid State Protonic Conductors
CountryUnited States
CitySanta Barbara, CA
Period15/08/1019/08/10
CitationsWeb of Science® Times Cited: 4

Keywords

  • Proton-conducting ceramic materials, Rare earth ortho-niobates, Acceptor-doped lanthanum niobate
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