Local Structure of Proton-Conducting Lanthanum Tungstate La_28-xW_4+xO_54+δ: a Combined Density Functional Theory and Pair Distribution Function Study

Journal Article · Wed Oct 02 00:00:00 EDT 2013 · Chemistry of Materials

DOI:https://doi.org/10.1021/cm401466r· OSTI ID:1088573

Kalland, Liv-Elisif; Magrasó, Anna; Mancini, Alessandro; Tealdi, Cristina; Malavasi, Lorenzo ^[1]

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1. Oslo

Lanthanum tungstate (La_28–xW_4+xO_54+δ) is a good proton conductor and exhibits a complex fluorite-type structure. To gain further understanding of the short-range order in the structure we correlate the optimized configurations obtained by density functional theory (DFT) with the experimental atomic pair distribution function analysis (PDF) of time-of-flight neutron and synchrotron X-ray data, collected at room temperature. The local atomic arrangements cannot be described by means of any average symmetric structure. Tungsten forms WO₆ octahedra in alternating directions, La1 is mainly 8-fold coordinated in relatively symmetric cubes, and La2 is coordinated with 6 or 7 oxygens in heavily distorted cubes. Both DFT and PDF confirm that the excess tungsten (x) is incorporated in La2 (1/4, 1/4, 1/4) sites in the La₂₇W₅O_55.5 composition. This additional tungsten can be considered as a donor self-dopant in the material and has implications to the conducting properties and the defect structure.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
• Sponsoring Organization: FOREIGN
• OSTI ID: 1088573
• Journal Information: Chemistry of Materials, Vol. 25, Issue (11) ; 06, 2013; ISSN 0897-4756
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: ENGLISH