Stabilization of cubic lithium-stuffed garnets of the type “Li7La3Zr2O12” by addition of gallium

► Li7La3Zr2O12 garnets, with cubic structure and fast lithium ion conductivity were stabilized by gallium addition. ► Materials with good sinterability, at low sintering time and temperature, were obtained. ► The new approach provides a quantitative and reproducible route of synthesis. ► Gallium addition stabilizes the cubic garnet phase at gallium content ≥0.3 moles per mole of Li7La3Zr2O12. ► Excess gallium, in the form of LiGaO2, resided at grain boundaries and acts as a sintering aid, which improves conductivity.