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@ARTICLE{Scherb:888334,
      author       = {Scherb, Tobias and Fantin, Andrea and Checchia, Stefano and
                      Stephan-Scherb, Christiane and Escolástico, Sonia and
                      Franz, Alexandra and Seeger, Janka and Meulenberg, Wilhelm
                      Albert and d'Acapito, Francesco and Serra, José M.},
      title        = {{U}nravelling the crystal structure of {N}d 5.8 {WO}
                      12−δ and {N}d 5.7 {W} 0.75 {M}o 0.25 {O} 12−δ mixed
                      ionic electronic conductors},
      journal      = {Journal of applied crystallography},
      volume       = {53},
      number       = {6},
      issn         = {1600-5767},
      address      = {[S.l.]},
      publisher    = {Wiley-Blackwell},
      reportid     = {FZJ-2020-04853},
      pages        = {},
      year         = {2020},
      abstract     = {Mixed ionic electronic conducting ceramics Nd6−yWO12−δ
                      (δ is the oxygen deficiency) provide excellent stability in
                      harsh environments containing strongly reactive gases such
                      as CO2, CO, H2, H2O or H2S. Due to this chemical stability,
                      they are promising and cost-efficient candidate materials
                      for gas separation, catalytic membrane reactors and protonic
                      ceramic fuel cell technologies. As in La6−yWO12−δ, the
                      ionic/electronic transport mechanism in Nd6−yWO12−δ is
                      expected to be largely controlled by the crystal structure,
                      the conclusive determination of which is still lacking. This
                      work presents a crystallographic study of Nd5.8WO12−δ and
                      molybdenum-substituted Nd5.7W0.75Mo0.25O12−δ prepared by
                      the citrate complexation route. High-resolution synchrotron
                      and neutron powder diffraction data were used in combined
                      Rietveld refinements to unravel the crystal structure of
                      Nd5.8WO12−δ and Nd5.7W0.75Mo0.25O12−δ. Both
                      investigated samples crystallize in a defect fluorite
                      crystal structure with space group Fm3m and doubled
                      unit-cell parameter due to cation ordering. Mo replaces W at
                      both Wyckoff sites 4a and 48h and is evenly distributed, in
                      contrast with La6−yWO12−δ. X-ray absorption
                      spectroscopy as a function of partial pressure pO2 in the
                      near-edge regions excludes oxidation state changes of Nd
                      (Nd3+) and W (W6+) in reducing conditions: the enhanced
                      hydrogen permeation, i.e. ambipolar conduction, observed in
                      Mo-substituted Nd6−yWO12−δ is therefore explained by
                      the higher Mo reducibility and the creation of additional
                      – disordered – oxygen vacancies.},
      cin          = {IEK-1},
      ddc          = {540},
      cid          = {I:(DE-Juel1)IEK-1-20101013},
      pnm          = {113 - Methods and Concepts for Material Development
                      (POF3-113)},
      pid          = {G:(DE-HGF)POF3-113},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {33304224},
      UT           = {WOS:000595702500008},
      doi          = {10.1107/S1600576720012698},
      url          = {https://juser.fz-juelich.de/record/888334},
}