Compounds with the perovskite structure were synthesized on the basis of the known high conductivity of the above titanates. Some compounds with Li in the A-site exhibited an ionic conductivity of more than 0.0001S/cm at room temperature. It was proposed that the high conductivity arose from the presence of a vacancy in the A-site, and from the existence of many equivalent sites for Li+ to occupy, or move between. The theory, that an increase in the free volume which was available to Li+ at A-sites, increased the Li ion conductivity, was proved in the case of the [(La½Li½)1-xSrx]TiO3 system. When x was equal to 0.05 or 0.1, the ionic conductivity was higher than that of the (La2/3-xLi3x)TiO3 system. In particular, when x was equal to 0.05, the ionic conductivity was equal to 0.0015S/cm at 300K. It was also noted that (Ln½Li½)TiO3 systems in which Ln3+ was smaller than La3+ exhibited lower Li ionic conductivities. This was suggested to support the above theory. It was concluded that not only the free volume available to Li+, but also the Li and vacancy concentrations in the A-site, played an important role in determining the ionic conductivity of the perovskite structure.

Y.Inaguma, L.Chen, M.Itoh, T.Nakamura: Solid State Ionics, 1994, 70-71, 196-202