Berlin 2001 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 7: Dynamics of Molecular Systems
CPP 7.5: Talk
Tuesday, April 3, 2001, 18:05–18:25, 112
Fluorine mobility in the superionic conductor LaF3: Field cycling and gradient NMR studies. — •Oliver Lips, Alexei Privalov, Mohammed Saad, and Franz Fujara — Institut für Festkörperphysik, TU-Darmstadt, 64283 Darmstadt, Germany
The tysonite structured solid electrolyte LaF3 possesses high fluorine mobility, which can be enhanced by heterovalent substitution of lanthanum. The mobility of fluorine is measured by means of mesoscopic and microscopic NMR techniques. With static field gradient NMR up to 1200K we obtained the self diffusion coefficient in several doped (0.01%-3% Sr) and pure crystals. A significant difference in the activation energy between pure and doped crystals has been found. Furthermore the dynamics in nominal pure crystals changes irreversibly after heating and the activation energy decreases from 1.25eV to approximately 0.2eV. On the microscopic scale field and temperature dependent spin-lattice relaxation time (T1) measurements are performed to examine the different motional processes.