| Autor: |
Brown, Alex J., Wagstaff, Oliver J., Evans, Ivana Radosavljevic, Evans, John S. O., Mole, Richard A., Wykes, Jeremy, Avdeev, Maxim, Ling, Chris D. |
| Zdroj: |
Chemistry of Materials; September 2024, Vol. 36 Issue: 17 p8188-8198, 11p |
| Abstrakt: |
The series Ba5R2Al2SnO13(R= In, Y, Er, Ho, Tb) has been synthesized and structurally characterized by X-ray and neutron powder diffraction. All members have oxygen-deficient 10-layer hexagonal (10H) perovskite-type structures at high temperature and gain mass on cooling equivalent to ∼0.5 oxygen atoms per formula unit, observed by both thermogravimetric analysis and the occupancy of a vacant site in the oxygen substructure refined against neutron powder diffraction data. The origin of this mass gain varies with R: for R= In, Y, Er, and Ho, it is due to water uptake via a hydroxylation mechanism to form Ba5R2Al2SnO13.xH2O (x≤ 0.5), with OH–ions occupying the vacant site and the other proton forming a second OH–in the oxygen substructure; while for R = Tb, it due to the oxidation of Tb3+to Tb4+, with O2–ions occupying the vacant site. These chemico-structural differences are consistent with the measured conductivity behavior of the samples, whereby Ba5Er2Al2SnO13is a proton conductor in air at moderate temperatures (∼10–4S cm–1at 500 °C) while Ba5Tb2Al2SnO13is a mixed oxide ionic and electronic conductor. These differences were further confirmed by X-ray absorption spectroscopy and corroborated by quasielastic neutron scattering. |
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