title: Lithium ion micrometer diffusion in a garnet-type cubic Li7La3Zr2O12(LLZO) studied using7Li NMR spectroscopy.
abstract: Mobile lithium ions in a cubic garnet Li7La3Zr2O12(Al-stabilized) were studied using7Li NMR spectroscopy for membrane and powder samples, the latter of which was ground from the membrane. Lithium diffusion in a micrometer space was measured using the pulsed-gradient spin-echo7Li NMR method between 70 and 130 °C. When the observation time (Δ) was shorter than 20 ms, the echo attenuation showed diffusive diffraction patterns, indicating that the Li+diffusing space is not free but restricted. For longer Δ, the values of apparent diffusion constant (Dapparent) became gradually smaller to approach an equilibrated value (close to a tracer diffusion constant). In addition, the Dapparentdepends on the pulse field gradient strength (g) and became smaller as g became larger. These experimental results suggest that the lithium ions diffuse through Li+pathways surrounded by stationary anions and lithium ions, and are affected by collisions and diffractions. One-dimensional profiles of the membrane sample of thickness 0.5 mm were observed from 65 to 110 °C and the area intensity, as well as the lithium occurrence near the surface, increased with the increase in temperature. The temperature-dependent area intensity showed a correspondence to the number of Li+carrier ions estimated from the ionic conductivity and the equilibrated diffusion constant through the Nernst-Einstein relationship.
authors.affiliation: Institute of Applied Physics, University of Tsukuba, Tennodai, Tsukuba 305-8573, Japan.
authors.forename: Kikuko
authors.initials: K
authors.lastname: Hayamizu
authors.affiliation: Material Science Laboratory, Central Research Institute of Electric Power Industry, Nagasaka, Yokosuka 240-0196, Japan.
authors.forename: Shiro
authors.initials: S
authors.lastname: Seki
authors.affiliation: MR Technology, Inc., Sengen, Tsukuba 300-0047, Japan.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Haishi