Journal Article

FZJ-2020-04853

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Unravelling the crystal structure of Nd 5.8 WO 12−δ and Nd 5.7 W 0.75 Mo 0.25 O 12−δ mixed ionic electronic conductors

Scherb, T. ; Fantin, A. (Corresponding author) ; Checchia, S. ; Stephan-Scherb, C. ; Escolástico, S. ; Franz, A. ; Seeger, J. ; Meulenberg, W. A.FZJ* ; d'Acapito, F. ; Serra, J. M.

2020
Wiley-Blackwell [S.l.]

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Please use a persistent id in citations: http://hdl.handle.net/2128/26323  doi:10.1107/S1600576720012698

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.

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Contributing Institute(s):

1. Werkstoffsynthese und Herstellungsverfahren (IEK-1)

Research Program(s):

1. 113 - Methods and Concepts for Material Development (POF3-113) (POF3-113)

Appears in the scientific report 2020

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Database coverage:
; ; ; Clarivate Analytics Master Journal List ; Current Contents - Physical, Chemical and Earth Sciences ; DEAL Wiley ; Ebsco Academic Search ; Essential Science Indicators ; IF < 5 ; JCR ; Nationallizenz ; PubMed Central ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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