Nuclear magnetic resonance in superionic conductors with fluorite-type structure

The 19 F NMR relaxation times T1 and T2 were measured in ternary and nonstoichiometric compounds with the fluorite-type structure. We have studied the Na0-4 Y0-6 F2-2 crystal in the temperature range 600 K to 900 K, where the crystal has not the fluorite structure. The T1 values were measured in 2 Larmor frequencies: 20.42 MHz and 34.24 MHz. The results for T1 were seem to be qualitatively similar to those measured in the system with two inequivalent sublattices. The T2 measurements, in the PbO84 Bi0-16 F2-16 crystal, were made during temperature cycles in the range of 300 K to 830 K. The difference in activation energy between cooling and heating half cycles, found to be approximately 0.08 eV, appear to be associated with the change in the clusters structure and not to the energy of defect formation. Finally, similar T2 measurements during temperature cycling was made in K0-4 Bi0-6 F2-2 : 2% Pb F2 crystal, in the temperature range 300 K to 800 K, but in this case no difference in the cooling and heating results was observed. We also measured, in the same temperature range, the T1 relaxation time in 3 Larmor frequencies: 11.71 MHz, 20.42 MHz and 34.24 Mhz. This results appear to indicate the existence of two hopping mechanism. (author). 132 refs., 68 figs