These garnet-like compounds formed a new class of solid-state Li-ion conductors with a novel crystal structure. The materials were prepared by solid-state reaction and were characterized by powder X-ray diffraction and alternating-current impedance in order to determine the Li-ion conductivity. The Nb and Ta compounds exhibited the same order of magnitude of bulk conductivity (about 10-6S/cm at 25C). The activation energies for ionic conductivity below 300C were 0.43 and 0.56eV for the Nb and Ta compounds, respectively.

Novel Fast Lithium Ion Conduction in Garnet-Type Li5La3M2O12 (M = Nb, Ta). V.Thangadurai, H.Kaack, W.J.F.Weppner: Journal of the American Ceramic Society, 2003, 86[3], 437-40