Nuclear magnetic resonance in superionics conductors with fluorite-type structure. / Ressonância magnética nuclear em condutores superiônicos de estrutura fluorita.

AUTOR(ES)
DATA DE PUBLICAÇÃO

1990

RESUMO

The 19F NMR relaxation times T1 and T2 were measured is ternary and nonstoichiometric compounds with the fluorite-type structure. We have studied the Na0.4Y0.6F2.2 crystal in the temperature range 600K to 900K, where the crystal hás not the fluorite structure. The T1 values were measured in two 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 measurement, in the Pb0.84Bi0.16F2.16 crystal, were made during temperature cycles in the range of 300K to 830K. The difference in activation energy between cooling and heating half cycles, found to be approximatly 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 the temperature cycling was made in K0.04Bi0.06 F2.2: 2% PbF2 crystal in the temperature range 300K to 800K, 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.

ASSUNTO(S)

fluorita rmn superiônicos condução iônica fluorite-type ion conductor superionics nmr

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