Influence of La₂Zr₂O₇ Additive on Densification and Li⁺ Conductivity for Ta-Doped Li₇La₃Zr₂O₁₂ Garnet

A high-conductivity solid electrolyte, La₂Zr₂O₇ (LZO) added to Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO), was prepared via conventional solid-state reactions and sintered at 1100°C for 10 h, which is tens of Celsius degrees lower than the typical sintering temperature for LLZTO. The addition of LZO did not bring in any impurities. LZO acted as a sintering aid to densify the LLZTO from a relative density of 77% up to 90%, which was comparable to that of pure LLZTO sintered at 1200°C. The 6 wt.% LZO–LLZTO samples sintered at 1100°C and 1200°C exhibited a room-temperature conductivity of 1.92 × 10⁻⁴ S/cm and 5.84 × 10⁻⁴ S/cm, respectively, which were higher than that of pure LLZTO samples. Glass-like phases observed at grain boundaries in LZO–LLZTO ceramics indicated that LZO promoted the formation of the glass-like phases binding together LLZTO grains and thus leading to enhanced density and conductivity of LLZTO.