Crystal structure and proton conductivity of BaSn0.6Sc0.4O3-delta: insights from neutron powder diffraction and solid-state NMR spectroscopy
Artikel i vetenskaplig tidskrift, 2016

The solid-state synthesis and structural characterisation of perovskite BaSn(1-x)ScxO(3-delta)(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 group Pm (3) over barm) with an increasing cell parameter as a function of scandium concentration along with some indication of phase segregation. Sn-119 and Sc-45 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). O-17 NMR spectra on O-17 enriched BaSn1-xScxO3-delta materials 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-delta refines the deuteron position at the 24k crystallographic site (x, y, 0) with x = 0.579(3) and y = 0.217(3) which leads to an O-D bond distance of 0.96(1) angstrom and suggests tilting of the proton towards the next nearest oxygen. Proton conduction was found to dominate in wet argon below 700 degrees C with total conductivity values in the range 1.8 x 10(-4) to 1.1 x 10(-3) S cm(-1) between 300 and 600 degrees 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 degrees C temperature region, and a suppression of the conductivity at higher temperature.



Chalmers, Kemi och kemiteknik, Energi och material

Stefan Norberg

Chalmers, Kemi och kemiteknik, Energi och material

Christopher Knee

Chalmers, Kemi och kemiteknik, Energi och material

Istaq Ahmed

Chalmers, Kemi och kemiteknik, Energi och material

S. Hull

STFC Rutherford Appleton Laboratory

L. Buannic

Stony Brook University

I. Hung

National High Magnetic Field Laboratory

Z. H. Gan

National High Magnetic Field Laboratory

F. Blanc

University of Liverpool

University of Cambridge

C. P. Grey

Stony Brook University

University of Cambridge

Sten Eriksson

Chalmers, Kemi och kemiteknik, Energi och material

Journal of Materials Chemistry A

20507488 (ISSN) 20507496 (eISSN)

Vol. 4 14 5088-5101





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