| 1. |
- Karlsson, Maths, 1978, et al.
(författare)
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Quasielastic neutron scattering of hydrated BaZr0.90A0.10O2.95 (A = Y and Sc)
- 2009
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738. ; 180:1, s. 22-28
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Tidskriftsartikel (refereegranskat)abstract
- Proton motions in hydrated proton conducting perovskites BaZr 0.90 A 0.10 O 2.95 (A = Y and Sc) have been investigated using quasielastic neutron scattering. The results reveal a localized motion on the ps time scale and with an activation energy of ~ 10-30 meV, in both materials. The temperature dependence of the total mean square displacement of the protons shows an onset of this motion at a temperature of about 300 K. The low activation energy, much lower than the activation energy for the macroscopic proton conductivity, suggests that this motion is not the rate-limiting process for the long-range proton diffusion, i.e. it is not linked to the two materials significantly different proton conductivities. In fact, a comparison of the QENS results with density functional theory calculations indicates that for both materials the observed motion may be ascribed to intra-octahedral proton transfers occurring close to a dopant atom. © 2008 Elsevier B.V. All rights reserved.
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| 2. |
- Karlsson, Maths, et al.
(författare)
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Short-range structure of proton-conducting perovskite BaInxZr1-xO3-x/2 (x=0-0
- 2009
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 20:10, s. 3480-3486
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Tidskriftsartikel (refereegranskat)abstract
- In a systematic study, we investigate the effect of dopant level and hydration on the short-range structure of the proton-conducting perovskite-type oxide BaInxZr1-xO3-x/2 (x = 0 - 0.75), using infrared and Raman spectroscopy. The results show that the doping leads to significant local distortions of the average cubic structure of these materials. By increasing the In concentration from x = 0 to x = 0.75, new bands appear and grow in intensity in both the IR and the Raman spectra, showing that the local distortions become successively more and more pronounced. The structural distortions are largely uncorrelated to the presence of oxygen vacancies, but instead are mainly driven by the size and charge difference between the In3+ and Zr4+ ions, which leads to displacements of the cations and to tilting of the (In/Zr)O-6 octahedra. On the basis of our results, we suggest that there is a threshold between x = 0.10 and x = 0.25 where the structural distortions propagate throughout the whole perovskite structure. Comparison of our spectroscopic data with the proton conductivity for the same materials indicates that the presence of extended structural distortions is favorable for fast proton transport.
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| 3. |
- Martinelli, Anna, 1978, et al.
(författare)
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Phase behavior and ionic conductivity in LiTFSI doped ionic liquids of the pyrrolidinium cation and TFSI anion
- 2009
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 113:32, s. 11247-11251
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Tidskriftsartikel (refereegranskat)abstract
- The phase behavior and the ionic conductivity of ionic liquids (ILs) of the N-alkyl-N-alkylpyrrolidinium (PYR xy ) cation and the bis(trifluoromethanesulfonyl)imide (TFSI) anion are investigated upon addition of LiTFSI salt. We compare the case of two new ILs of the PYR 2y cation (where 2 is ethyl and y is butyl or propyl) with that of the PYR 14 (where 1 is methyl and 4 is butyl). We find that the addition of LiTFSI increases the glass transition temperature, decreases the melting temperature and the heat of fusion and, in the ILs of the PYR 2y family, suppresses crystallization. In the solid state, significant ionic conductivities are found, being as high as 10 -5 Scm -1 , strongly increasing with Li + concentration. The opposite trend is found in the liquid state, where the conductivity is on the order of 10 -3 -10 -2 Scm -1 at room temperature. A T g -scaled Arrhenius plot shows that the liquid-state ionic conductivity in these systems is mainly governed by viscosity and that the fragility of the liquids is slightly influenced by the structural modifications on the cation. © 2009 American Chemical Society.
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