Spin relaxation and ultra-slow Li motion in an aluminosilicate glass ceramic.
The ion dynamics in a lithium aluminosilicate glass ceramic was studied using stimulated-echo 7Li-NMR. For temperatures 300 K<T<450 K the hopping correlation times, tau(C), were determined from the decay of the quadrupolar spin-alignment amplitude. The decay times were thermally activated with an energy barrier of 0.61 eV, in agreement with conductivity measurements. For T<300 K the temperature dependence of the decay times, now corresponding to T1Q, was much weaker. The T1Q times followed the same trend as the independently measured spin-lattice relaxation times, T1, but were a factor of about three shorter than those. The theoretical ratio of T1/T1Q is shown to be 25/8 in the slow-motion regime if quadrupolar spin relaxation prevails. This result explains the present observation and similar ones made for several Li ion conductors. The relaxation of the octupolar spin-alignment order is discussed.
Böhmer
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Experimentelle Physik III, Fachbereich Physik and Interdisziplinäres Zentrum für Magnetische Resonanz, Universität Dortmund, 44221 Dortmund, Germany. Roland.Bohmer@Uni-Dortmund.de
Qi
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D000535:Aluminum / Q000737:chemistry*; D000538:Aluminum Silicates / Q000737:chemistry*; D002516:Ceramics / Q000737:chemistry*; D003198:Computer Simulation; D004058:Diffusion; D005898:Glass / Q000737:chemistry*; D008094:Lithium / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D009038:Motion; D011522:Protons; D013113:Spin Labels
D000538:Aluminum Silicates; D011522:Protons; D013113:Spin Labels; C049037:aluminosilicate; D008094:Lithium; D000535:Aluminum