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Ion Conduction (ion + conduction)

Distribution by Scientific Domains

Polymers and Materials Science	75%

Selected Abstracts

Comprehensive Modeling of Ion Conduction of Nanosized CaF2/BaF2 Multilayer Heterostructures

ADVANCED FUNCTIONAL MATERIALS, Issue 1 2009
Xiangxin Guo
Abstract Molecular beam epitaxy-grown CaF2/BaF2 heterolayers are a demonstration of the potential of nanoionics. It has been shown that ion conductivities both parallel and perpendicular to the interfaces increase with decrease in interfacial spacing. This size effect was attributed to the thermodynamically necessary redistribution of the mobile fluoride ions (N. Sata, K. Eberl, K. Eberman, J. Maier, Nature 2000, 408, 946; X. X. Guo, I. Matei, J.-S. Lee, J. Maier, Appl. Phys. Lett. 2007, 91, 103102). On this basis, the striking phenomenon of an upward bending in the effective parallel conductivity as a function of inverse interfacial spacing for low temperatures (T,,,593,K) has been satisfactorily explained by application of a modified Mott,Schottky model for BaF2 (X.X. Guo, I. Matei, J. Jamnik, J.-S. Lee, J. Maier, Phys. Rev. B 2007, 76, 125429). This model was further confirmed by measurements perpendicular to the interfaces that offer complementary information on the more resistive parts. Here a successful comprehensive modeling of parallel and perpendicular conductivities for the whole parameter range, namely for interfacial spacings ranging from 6 to 200,nm and investigated temperatures ranging from 455 to 833,K, is presented. The model is based on literature data for carrier mobilities and Frenkel reaction constants and the assumption of a pronounced F, redistribution. Given the fact that an impurity content that was experimentally supported is taken into account and apart from minor assumptions concerning profile homogeneity, the only fit parameter is the space charge potential. In particular, it is worth mentioning that in BaF2 the low temperature Mott,Schottky space charge zone which is determined by impurities changes over, at high temperatures, into a Gouy,Chapman situation owing to increased thermal disorder. (The situation in CaF2 is of Gouy,Chapman type at all temperatures.) [source]

ChemInform Abstract: A Discovery of Tetravalent Ge4+ Ion Conduction in Solids.

CHEMINFORM, Issue 42 2009
Naoyoshi Nunotani
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Ionically Conducting Two-Dimensional Heterostructures

ADVANCED MATERIALS, Issue 25-26 2009
Xiangxin Guo
Abstract In the context of revealing interfacial effects on ion conduction, thin films are extremely worthwhile due to defined geometry. Of particular interest are heterostructures as they offer symmetric boundary conditions and a high density of hetero-interfaces. The recent progress in this field is reviewed. Materials classes under concern include halides and oxides, and refer to various degrees of disorder and different mobilities. Even though in its infancy, the field of ionic heterostructures is already characterized by a variety of results of fundamental importance and of technological relevance. [source]

Highly conductive, oriented polymer electrolytes for lithium batteries,

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 10-12 2002
D. Golodnitsky
Abstract In semicrystalline complexes of poly(ethylene oxide) (PEO) with different salts, such as lithium iodide, lithium trifluoromethanesulfonate (LiTF) and lithium trifluoromethanesulfonimide (LiTFSI), stretching induced longitudinal DC conductivity enhancement was observed, in spite of the formation of more ordered polymer electrolyte (PE) structure. It was found that the more amorphous the PE, the less its lengthwise conductivity is influenced by stretching. The results of our investigation suggest that ionic transport occurs preferentially along the PEO helical axis, at least in the crystalline phase, and that the rate-determining step of the lithium ion conduction in LiI:P(EO)20, LiTF:P(EO)20 polymer electrolytes below Tm is "interchain" hopping. Understanding ion transport processes is clearly a fertile field for research and development in the synthesis of new rigid polymers with ordered channels and composition appropriate for enhanced ionic conductivity. Copyright © 2003 John Wiley & Sons, Ltd. [source]