Cubic A-site deficient Sr0.5+xLi0.5−2x□xMO3 and La-doped Sr0.55−1.5xLaxLi0.4□0.5x+0.05MO3, Sr0.575−1.5xLaxLi0.35□0.5x+0.075MO3 and Sr0.6−1.5xLaxLi0.3□0.5x+0.1MO3 perovskites (M = Ti0.5Ta0.5) were synthesized and their Li-ion conductivities were determined. Among these compounds, the highest ionic conductivity (7.2 x 10−4S/cm at 294K) was found for Sr0.55−1.5xLaxLi0.4□0.5x+0.05MO3 (x = 0.05). In Sr0.5+xLi0.5−2x□xTi0.5Ta0.5O3, the lattice constants were independent of the composition, and the compositional dependence of the ionic conductivity indicated that the conduction mechanism involved the vacancy diffusion process of the Li ions and vacancies that percolated through the A-site sub-lattice; including the skeletal ions, Sr2+, as obstacles. On the other hand, in La-doped systems the compositional dependence of the ionic conductivity was found to be associated with a vacancy diffusion process including site percolation, and a reduction in bottleneck size - due to the substitution of La - that depressed the conductivity. It was also found that the activation energy derived from the direct-current conductivity was influenced by long-range cooperative ionic motion, together with factors such as the bottleneck size.

Synthesis and Lithium Ion Conductivity of Cubic Deficient Perovskites Sr0.5+xLi0.5−2xxTi0.5Ta0.5O3 and the La-Doped Compounds. Y.Inaguma, A.Seo, T.Katsumata: Solid State Ionics, 2004, 174[1-4], 19-26