IONIC-CONDUCTION OF LITHIUM FOR PEROVSKITE-TYPE COMPOUNDS, (LI0.05LA0.317)(1-X)SR0.5XNBO3, (LI0.1LA0.3)(1-X)SR0.5XNBO3 AND (LI0.25LA0.25)(1-X)M0.5XNBO3 (M=CA AND SR)

In order to improve the ionic conductivity of lithium in the (Li, La)N bO3 perovskite system due to the expansion of the lattice, we attempte d 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 i n Li0.05La0.317NbO3 (orthorhombic), Li0.1La0.3NbO3 (tetragonal) and Li 0.25La0.25NbO3 (cubic), respectively. Also, the perovskite compounds ( Li0.25La0.25)(1-x)Ca0.5xNbO3 were prepared by the substitution of smal ler Ca2+ ions for larger La3+ ions for comparison. The enhancement of lithium ionic conductivity was confirmed in all the Sr2+ doped perovsk ite compounds because of the increase of the cell volume. Especially, the perovskite (Li0.25La0.25)(1-x)Sr0.5xNbO3 exhibited marked improvem ent of ionic conductivity (x = 0.125, 7.3 x 10(-5) S.cm(-1) at 25 degr ees 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 io nic conductivity of (Li0.25La0.25)(1-x)Ca0.5xNbO3 perovskite compounds decreased with increasing the amount of calcium due to the decrease o f the cell volume. (C) 1998 Elsevier Science B.V. All rights reserved.