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

Francis G. Kinyanjui (Institutionen för kemi och kemiteknik, Oorganisk miljökemi) ; Stefan T. Norberg (Institutionen för kemi och kemiteknik, Oorganisk miljökemi) ; Christopher S Knee (Institutionen för kemi och kemiteknik, Oorganisk miljökemi) ; Istaq Ahmed (Institutionen för kemi och kemiteknik, Oorganisk miljökemi) ; S. Hull ; L. Buannic ; I. Hung ; Z. H. Gan ; F. Blanc ; C. P. Grey ; Sten G. Eriksson (Institutionen för kemi och kemiteknik, Oorganisk miljökemi)
Journal of Materials Chemistry A (2050-7488). Vol. 4 (2016), 14, p. 5088-5101.
[Artikel, refereegranskad vetenskaplig]

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.

Denna post skapades 2016-04-29. Senast ändrad 2016-08-22.
CPL Pubid: 235614


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Institutionen för kemi och kemiteknik, Oorganisk miljökemi



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