Effect of sintering process on the microstructure and ionic conductivity of Li7–La3Zr2–Ta O12 ceramics

Li7–xLa3Zr2–xTaxO12 (0 ≤ x ≤ 1) ceramics were prepared by pressureless sintering at 1230 °C in air. XRD, SEM and Impedance test were used to characterize the crystal structure, microstructure and electrical performance of Li7–xLa3Zr2–xTaxO12 ceramics. According to XRD data, the specimens with x ≥ 0.2 sintered at 1230 °C for 1 h exhibit a cubic garnet structure without impurities. The Ta-doped specimens sintered at 1230°C for 1 h show high relative density of 91.6%–93.9%. Ta doping has a certain effect on the Li vacancy concentration, lithium arrangement, movable Li+ concentration and microstructure of the LLZO ceramic. The Li6.6La3Zr1.6Ta0.4O12 ceramic sintered at 1230°C for 1 h has the highest total conductivity of 6.01 × 10–4 S·cm–1 at room temperature and the lowest activation energy of 0.27 eV.