Effect of B-Site Substitution of (Li,La)TiO3 Perovskites by Di-, Tri-, Tetra- and Hexavalent Metal Ions on the Lithium Ion Conductivity

We report the synthesis and lithium ion conductivity of di-, tri-, tetra-and hexavalent metal ion B-site substituted (Li,La)TiO(3) (LLT) perovskites. All 5-10 mol% Mg, Al, Mn, Ge, Ru and W ion substituted LLTs crystallize in a simple cubic or tetragonal perovskite structure. Among the oxides investigated, the Al-substituted perovskite La(0.55)Li(0.36)square(0.09)Ti(0.995)Al(0.005)O(3) (square = vacancy) exhibits the highest lithium ion conductivity of 1.1 x 10(-3) S/cm at room temperature which is slightly higher than that of the undoped (Li,La) TiO(3) perovskite (8.9 x 10(4) S/cm) at the same temperature. The lithium ion conductivity of substituted LLTs does not seem to depend on the concentration of the A-site ion vacancies and unit cell volume. The high ionic conductivity of Al-substituted LLT is attributed to the increase of the B(Al)-O bond and weakening of the A(Li, La)-O bond. The conductivity behavior of the doped LLT is being described on the basis of Gibbs free energy considerations.