DEPENDENCE OF THE LITHIUM IONIC-CONDUCTIVITY ON THE B-SITE ION SUBSTITUTION IN (LI0.5LA0.5)TI1-XMXO3 (M = SN, ZR, MN, GE)

The dependence of the ionic conductivity on the B-site ion substitutio n in (Li0.5La0.5)Ti1-xMxO3 (M = Sn, Zr, Mn, Gel system has been studie d. The same valence state and various electronic configurations and io nic radii of Sn4+, Zr4+, Mn4+ and Ge4+ (4d(10) (0.69 Angstrom), 4p(6) (0.72 Angstrom), 3d(10) (0.54 Angstrom) and 3d(3) (0.54 Angstrom), res pectively) induced the various crystallographic variations with substi tutions. So it was possible to investigate the crystallographic factor s which influence the ionic conduction by observing the dependence of the conductivity on the crystallographic variations. We found that the conductivity increased with decreasing the radii of B-site ions and v ice versa and octahedron distortion disturbs the ion conduction. The r eason for this reciprocal relationship of conductivity on the radius o f B-site ions has been examined on the basis of the interatomic bond s trength change due to the cation substitutions. The results were in go od agreement with the experimental results. Therefore it could be conc luded that interatomic bond strength change due to the cation substitu tions may be one of the major factors influencing the lithium ion cond uctivity in the perovskite (Li0.5La0.5)TiO3 system.