Relationship between lithium content and ionic conductivity in the Li5 + 2xLa3Nb2 − xScxO12 system

• Single phase garnet-like Li5 + 2xLa3Nb2 − xScxO12 was synthesized in x = 0–0.75.
• Magnesia crucible was effective to eliminated contamination in the samples.
• Lithium ion conductivity increased with the lithium content.
• An average bulk conductivity of ca. 3.5 × 10− 4 S cm− 1 was obtained at 25 °C.

The Al-free cubic garnet-like Li5 + 2xLa3Nb2 − xScxO12 series with x = 0–0.75 was successfully synthesized by solid state reaction. Final sintering at 1150 °C for 12 h in a magnesia crucible with the mother powder method resulted in stoichiometric single phases that corresponded to each nominal composition. The conductivity of the samples showed a positive dependency on the Li content and the optimum Li content for Li conduction was 6.25–6.5 in the formula unit. The highest bulk conductivity of 3.70 × 10− 4 S cm− 1 was observed for x = 0.625 at 25 °C and that for x = 0.75 at 50 °C was 6.05 × 10− 4 S cm− 1.