Lithium garnet-type oxides Li7−xLa3(Zr2−x, Nbx)O12 (x = 0–2) were synthesized by a solid-state reaction, and their lithium ion conductivity was measured using an AC impedance method at temperatures ranging from 25 to 150C in air. The lithium ion conductivity increased with increasing Nb content, and reached a maximum of about 0.8mS/cm at 25C. By contrast, the activation energy reached a minimum of about 30kJ/mol at the same point with X = 0.25. The potential window was examined by cyclic voltammetry, which showed lithium deposition and dissolution peaks around 0V vs. Li+/Li, but showed no evidence of other reactions up to 9V vs. Li+/Li.

High Lithium Ionic Conductivity in the Garnet-Type Oxide Li7-xLa3(Zr2−x,Nbx)O12 (x = 0–2). S.Ohta, T.Kobayashi, T.Asaoka: Journal of Power Sources, 2011, 196[6], 3342-5