Ionic conduction of lithium for perovskite type compounds, (Li0.05La0.317)1-xSr0.5xNbO3, (Li0.1La0.3)1-xSr0.5xNbO3 and (Li0.25La0.25)1-xM0.5xNbO3 (M=Ca and Sr)

In order to improve the ionic conductivity of lithium in the (Li, La)NbO3 perovskite system due to the expansion of the lattice, we attempted to prepare three perovskite compounds (Li0.05La0.317)(1-x)Sr0.5xNbO3, (Li0.1La0.3)(1-x)Sr0.5xNbO3 and (Li0.25La0.25)(1-x)Sr0.5xNbO3 by the substitution of larger Sr2+ ions for smaller Lif ions and La3+ ions in Li0.05La0.317NbO3 (orthorhombic), Li0.1La0.3NbO3 (tetragonal) and Li0.25La0.25NbO3 (cubic), respectively. Also, the perovskite compounds (Li0.25La0.25)(1-x)Ca0.5xNbO3 were prepared by the substitution of smaller Ca2+ ions for larger La3+ ions for comparison. The enhancement of lithium ionic conductivity was confirmed in all the Sr2+ doped perovskite compounds because of the increase of the cell volume. Especially, the perovskite (Li0.25La0.25)(1-x)Sr0.5xNbO3 exhibited marked improvement of ionic conductivity (x = 0.125, 7.3 x 10(-5) S.cm(-1) at 25 degrees C) compared with that of the other perovskites ((Li0.05La0.317)(1-x)Sr0.5xNbO3 and (Li0.1La0.3)(1-x)Sr0.5xNbO3), on the contrary, the ionic conductivity of (Li0.25La0.25)(1-x)Ca0.5xNbO3 perovskite compounds decreased with increasing the amount of calcium due to the decrease of the cell volume. (C) 1998 Elsevier Science B.V. All rights reserved.