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New prospects in studying Li diffusion—two-time stimulated echo NMR of spin-3/2 nuclei
Institution:1. Blackett Laboratory, Imperial College, London SW7 2AZ, England, UK;2. Center for Quantum Spacetime, Sogang University, Seoul 121-742, Republic of Korea;3. Department of Applied Mathematics and Theoretical Physics, Cambridge, CB3 0WA, England, UK;1. Institut de Chimie de Strasbourg (UMR 7177, CNRS-Unistra), Université de Strasbourg, 4 rue Blaise Pascal, CS 90032, F-67081 Strasbourg, France;2. Department of Natural Sciences, University of Michigan – Dearborn, 4901 Evergreen Rd, Dearborn, MI 48128, United States;3. Department of Chemistry, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus;4. Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 76100, Israel;1. UNB MRI Centre, Department of Physics, University of New Brunswick, Fredericton, New Brunswick E3B 5A3, Canada;2. Department of Chemistry, McMaster University, Hamilton, Ontario L8S 4L8, Canada;3. Department of Chemistry, University of New Brunswick, P.O. Box 4400, Fredericton, New Brunswick E3B 5A3, Canada
Abstract:The measurement of diffusion parameters like activation energies and translational jump rates of small cations plays a key role in materials science. Especially the in-depth investigation of Li diffusion in ionic conductors is of great interest, because suitable ionic conductors are needed for, e.g., the development of new secondary ion battery systems. As the standard tracer method is not applicable to study Li diffusion due to the lack of a suitable radioactive isotope, Li diffusion is alternatively probed by solid state NMR techniques. With the different NMR methods being available, diffusion processes can be studied on different length- and timescales. In the present paper we use two-time spin-alignment echo (SAE) NMR for the direct, i.e., model independent, measurement of extremely small translational Li jump rates. To this end, different crystalline and glassy ion conductors like LixTiS2, Li4SiO4 as well as LiNbO3 served as model substances to reveal the special features of this technique. SAE-NMR, which was originally developed for deuterons, has also been applied in a few cases to spin-3/2 nuclei, like 7Li, before. The corresponding correlation functions yield not only information about diffusion parameters but also about geometric properties of the diffusion pathways, making SAE-NMR a powerful method which complements well-established NMR techniques.
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