Effect of sintering process on the microstructure and ionic conductivity of Li_7–xLa₃Zr_2–xTa_xO₁₂ ceramics

Li_7–xLa₃Zr_2–xTa_xO₁₂ (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 Li_7–xLa₃Zr_2–xTa_xO₁₂ 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 Li_6.6La₃Zr_1.6Ta_0.4O₁₂ 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.