Effect of Y substitution for Nb in Li5La3Nb2O12 on Li ion conductivity of garnet-type solid electrolytes

We report the effect of Y substitution for NI) on Li ion conductivity in the well-known garnet-type Li5La3Nb2O12. Garnet-type Li5La3Nb2-xYxO12-delta (0 <= x <= 1) was prepared by ceramic method using the high purity metal oxides and salts. Powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), Li-7 nuclear magnetic resonance (Li NMR) and AC impedance spectroscopy were employed for characterization. PXRD showed formation of single-phase cubic garnet-like structure for x up to 0.25 and above x=0.25 showed impurity in addition to the garnet-type phases. The cubic lattice constant increases with increasing V content up to x=0.25 in Li(5)La(3)Nb(2-x)Y(x)O12-delta and is consistent with expected ionic radius trend. Li-7 MAS NMR showed single peak, which could be attributed to fast migration of ions between various sites in the garnet structure, close to chemical shift 0 ppm with respect to solid LiCl and which confirmed that Li ions are distributed at an average octahedral coordination in Li5La3Nb2-xYxO12-delta. Y-doped compounds showed comparable electrical conductivity to that of the parent compound Li5La3Nb2O12. The x=0.1 member of Li5La3Nb2-xYxO12-delta showed total (bulk + grain-boundary) ionic conductivity of 1.44 x 10(-5) Scm(-1) at 23 degrees C in air. (C) 2011 Elsevier B.V. All rights reserved.