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- Hall, Andreas, 1975
(författare)
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Ionic Conduction and Bond Valence in Glasses
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ion conducting glasses are highly interesting for several different applications, among them, chemical sensors, smart windows with variable optical properties and as electrolytes in batteries. The last example can take full advantage of the ease with which a thin film (
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- Hall, Andreas, 1975, et al.
(författare)
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Mixed mobile ion effect and cooperative motions in silver-sodium phosphate glasses
- 2008
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Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 101:19, s. 195901-
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Tidskriftsartikel (refereegranskat)abstract
- The conduction pathways and the extraordinary weak mixed mobile ion effect (MMIE) in AgxNa1-xPO3 glasses have been investigated by bond-valence analysis of reverse Monte Carlo produced structural models. We find that the MMIE is suppressed in this system due to a common cooperative hopping process, where both Ag and Na participate. This finding is in strong contrast to glass systems exhibiting a pronounced MMIE, where the two types of mobile ions have distinctly different conduction pathways and the M ions tend to block the pathways for the N ions and vice versa. © 2008 The American Physical Society.
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- Hall, Andreas, 1975, et al.
(författare)
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Structure of Ag x Na 1−x PO 3 glasses by neutron diffraction and reverse Monte Carlo modelling
- 2007
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Ingår i: Journal of Physics Condensed Matter. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 19:41
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Tidskriftsartikel (refereegranskat)abstract
- We have performed structural studies of mixed mobile ion phosphate glasses Ag x Na 1−x PO 3 using diffraction experiments and reverse Monte Carlo simulations. This glass system is particularly interesting as a model system for investigations of the mixed mobile ion effect, due to its anomalously low magnitude in the system. As for previously studied mixed alkali phosphate glasses, with a much more pronounced mixed mobile ion effect, we find no substantial structural alterations of the phosphorous–oxygen network and the local coordination of the mobile cations. Furthermore, the mobile Ag + and Na + ions are randomly mixed with no detectable preference for either similar or dissimilar pairs of cations. However, in contrast to mixed mobile ion systems with a very pronounced mixed mobile ion effect, the two types of mobile ions have, in this case, very similar local environments. For all the studied glass compositions the average Ag–O and Na–O distances in the first coordination shell are determined to be 2.5 ± 0.1 and 2.5 ± 0.1 Å, and the corresponding average coordination numbers are approximately 3.2 and 3.7, respectively. The similar local coordinations of the two types of mobile ions suggests that the energy mismatch for a Na + ion to occupy a site that previously has been occupied by a Ag + ion (and vice versa) is low, and that this low energy mismatch is responsible for the anomalously weak mixed mobile ion effect. (Some figures in this article are in colour only in the electronic version).
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- Karlsson, Maths, 1978, et al.
(författare)
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Structure of Proton-Conducting Alkali Thio-Hydroxogermanates
- 2008
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 1520-5002 .- 0897-4756. ; 20:19, s. 6014-6021
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Tidskriftsartikel (refereegranskat)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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