wang hay kan - Synthesis, Rietveld refinement of crystal structure, electron diffraction, and electrical transport properties of Ba2(Ca1–x–yFexNby)(Nb1–zFez)O6–δ double perovskites

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      Wang Hay Kan, Trang T. Trinh, Tobias Fürstenhaupt, Venkataraman   Thangadurai

      Can. J. Chem.  2011, 89, 688.


      We report the synthesis, crystal structure, and electrochemical   properties of new Fe-doped   Ba2(Ca1–xyFexNby)(Nb1–zFez)O6–δ  (Fe–BCN). The Fe–BCN was synthesized by a solid-state method in   air using corresponding metal oxides and salts at elevated   temperature. All of the observed powder X-ray diffraction (PXRD)   peaks of the investigated Fe–BCN were indexed as cubic   Fm-3m (space group No. 225) double   perovskite-type structure with cell constants a    8.4 Å and is consistent with selected area electron diffraction   (SAED). Rietveld analysis suggested the distribution of Fe was at   both 4a and 4b sites, supported the proposed   chemical formula   Ba2(Ca1–xyFexNby)(Nb1–zFez)O6–δ.   This was further verified by bond valence sum (BVS) analysis of   the cations. The Fe–BCN showed superior chemical stability in   pure CO2 and boiling H2O confirmed by PXRD   and FTIR. The electrical conductivity was determined by AC   impedance spectroscopy. Among the samples investigated,   Ba2(Ca0.79Fe0.21)(Nb0.71Fe0.29)O6–δ  showed the highest total (bulk + grain-boundary) conductivity of   1.1 × 10−2 S cm–1 in humidified (3%)   N2 at 600 °C with activation energy of 0.43 eV in the   temperature range 200–800 °C.

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