title: Crystal structure and proton conductivity of BaSn0.6Sc0.4O3-δ: insights from neutron powder diffraction and solid-state NMR spectroscopy.
abstract: The solid-state synthesis and structural characterisation of perovskite BaSn1-xScxO3-δ(x= 0.0, 0.1, 0.2, 0.3, 0.4) and its corresponding hydrated ceramics are reported. Powder and neutron X-ray diffractions reveal the presence of cubic perovskites (space groupPm3m) with an increasing cell parameter as a function of scandium concentration along with some indication of phase segregation.119Sn and45Sc solid-state NMR spectroscopy data highlight the existence of oxygen vacancies in the dry materials, and their filling upon hydrothermal treatment with D2O. It also indicates that the Sn4+and Sc3+local distribution at the B-site of the perovskite is inhomogeneous and suggests that the oxygen vacancies are located in the scandium dopant coordination shell at low concentrations (x≤ 0.2) and in the tin coordination shell at high concentrations (x≥ 0.3).17O NMR spectra on17O enriched BaSn1-xScxO3-δmaterials show the existence of Sn-O-Sn, Sn-O-Sc and Sc-O-Sc bridging oxygen environments. A further room temperature neutron powder diffraction study on deuterated BaSn0.6Sc0.4O3-δrefines the deuteron position at the 24k crystallographic site (x,y, 0) withx= 0.579(3) andy= 0.217(3) which leads to an O-D bond distance of 0.96(1) Å and suggests tilting of the proton towards the next nearest oxygen. Proton conduction was found to dominate in wet argon below 700 °C with total conductivity values in the range 1.8 × 10-4to 1.1 × 10-3S cm-1between 300 and 600 °C. Electron holes govern the conduction process in dry oxidizing conditions, whilst in wet oxygen they compete with protonic defects leading to a wide mixed conduction region in the 200 to 600 °C temperature region, and a suppression of the conductivity at higher temperature.
authors.affiliation: Department of Chemical and Biological Engineering , Chalmers University of Technology , SE-412 96 Gothenburg , Sweden.
authors.forename: Francis G
authors.initials: FG
authors.lastname: Kinyanjui
authors.affiliation: Department of Chemical and Biological Engineering , Chalmers University of Technology , SE-412 96 Gothenburg , Sweden.
authors.forename: Stefan T
authors.initials: ST
authors.lastname: Norberg
authors.affiliation: Department of Chemical and Biological Engineering , Chalmers University of Technology , SE-412 96 Gothenburg , Sweden.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Knee
authors.affiliation: Department of Chemical and Biological Engineering , Chalmers University of Technology , SE-412 96 Gothenburg , Sweden.
authors.forename: Istaq
authors.initials: I
authors.lastname: Ahmed
authors.affiliation: The ISIS Facility , STFC Rutherford Appleton Laboratory , Didcot , Oxfordshire OX11 0QX , UK.
authors.forename: Stephen
authors.initials: S
authors.lastname: Hull
authors.affiliation: Department of Chemistry , State University of New York , Stony Brook , NY 11790-3400 , USA.
authors.forename: Lucienne
authors.initials: L
authors.lastname: Buannic
authors.affiliation: Center of Interdisciplinary Magnetic Resonance , National High Magnetic Field Laboratory , 1800 East Paul Dirac Drive , Tallahassee , Florida 32310 , USA.
authors.forename: Ivan
authors.initials: I
authors.lastname: Hung
authors.affiliation: Center of Interdisciplinary Magnetic Resonance , National High Magnetic Field Laboratory , 1800 East Paul Dirac Drive , Tallahassee , Florida 32310 , USA.
authors.forename: Zhehong
authors.initials: Z
authors.lastname: Gan
authors.affiliation: Department of Chemistry , University of Cambridge , Lensfield Road , Cambridge , CB2 1EW , UK ; Department of Chemistry and Stephenson Institute for Renewable Energy , University of Liverpool , Crown Street , Liverpool , L69 7ZD , UK.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Blanc
authors.affiliation: Department of Chemistry , State University of New York , Stony Brook , NY 11790-3400 , USA ; Department of Chemistry , University of Cambridge , Lensfield Road , Cambridge , CB2 1EW , UK.
authors.forename: Clare P
authors.initials: CP
authors.lastname: Grey
authors.affiliation: Department of Chemical and Biological Engineering , Chalmers University of Technology , SE-412 96 Gothenburg , Sweden.
authors.forename: Sten G
authors.initials: SG
authors.lastname: Eriksson