| 1. |
- Karlsson, Maths, et al.
(author)
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Short-range structure of proton-conducting perovskite BaInxZr1-xO3-x/2 (x=0-0
- 2009
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In: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 20:10, s. 3480-3486
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Journal article (peer-reviewed)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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| 2. |
- Karlsson, Maths, 1978, et al.
(author)
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Structure of Proton-Conducting Alkali Thio-Hydroxogermanates
- 2008
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In: Chemistry of Materials. - : American Chemical Society (ACS). - 1520-5002 .- 0897-4756. ; 20:19, s. 6014-6021
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Journal article (peer-reviewed)abstract
- Using a combination of neutron diffraction, infrared spectroscopy, and first-principles calculations, we have investigated the structure of hydrated and dehydrated proton conducting alkali thio-hydroxogermanates of general formula M2GeS2(OH)2·yH2O (M = K, Rb, and Cs). The results show that the structure of hydrated and dry materials are basically the same, which confirms previous indications that the main effect of heating these materials is just a loss of water. We suggest that in the hydrated state the structure of these materials is built of dimers of thio-hydroxogermanate anions, with the water molecules acting as bridges between such dimers. In the dehydrated structure, the thio-hydroxogermanate anions instead form an extended network through the formation of interdimer hydrogen bonds through the −OH groups in the structure. The alkali ions are suggested to act as “space-fillers” in voids formed by the thio-hydroxogermanate anion dimers, in both the hydrated and the dehydrated state.
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