Ceramic superconductor samples were lithiated by reaction with n-butyl-lithium. When the nominal Li content was less than unity per formula, the presence of so-called ‘123’ and ‘124’ phases was deduced from X-ray diffraction and high-resolution electron microscopic data. Nuclear magnetic resonance and impedance spectroscopic techniques were applied to a sample with a nominal Li content of 0.9 per formula. The spin-lattice relaxation times and electrical conductivity relaxations were measured as a function of temperature. The results were interpreted in terms of a stretched exponential decay function in the time domain. Microscopic activation energies of 0.49eV (nuclear magnetic resonance measurements) and 0.41eV (electrical conductivity relaxation data) were deduced for short-range Li motion. The activation energies for long-range motion were 0.98eV (nuclear magnetic resonance) and 1.03eV (electrical conductivity relaxation).

A.Várez, C.León, J.Santamaría, J.M.Rojo, J.Sanz, E.Morán, F.Sánchez-Quesada, M.A.Alario-Franco: Journal of Physics - Condensed Matter, 1995, 7[28], 5477-89