Li diffusive behavior of garnet-type oxides studied by muon-spin relaxation and QENS.

Abstract: A diffusive behavior of Li+ ion in a garnet-type oxide, Li5+ x La3Zr x Nb2−x012 with x =0–2, has been investigated by both a positive muon-spin relaxation (μ +SR) and quasi-elastic neutron scattering (QENS) technique using powder samples. The μ +SR results revealed that Li+ ions start to diffuse above ~150K for the whole samples measured. The activation energy of Li diffusion (Ea ) estimated from the μ +SR data was in good agreement with Ea obtained by the QENS measurements. However, both Ea s were about a half of Ea of ionic conductivity of Li+ (σ Li), which was evaluated by AC-impedance measurements on sintered pellets. This indicated the serious effect of grain boundary and/or surface on Ea . Furthermore, since the diffusion coefficient of Li+ estimated by μ +SR is roughly independent of x, the number of mobile Li+ in the garnet lattice was found to be the predominant parameter to determine σ Li. [Copyright &y& Elsevier]