Sintering, micro-structure and Li+ conductivity of Li7−xLa3Zr2−xNbxO12/MgO (x = 0.2–0.7) Li-Garnet composite ceramics.

Abstract Nb-doped Li 7 La 3 Zr 2 O 12 (Nb-LLZO) is one of the promising electrolyte candidates in the Li-Garnet family due to its high Li-ion conductivity. The sintered Nb-LLZO ceramics, however, often exhibit abnormal grain growth with high porosity and poor mechanical properties. For advantaged electrochemical and mechanical properties, a uniform and dense microstructure is desired. In this research, MgO has been added as a secondary phase to inhibit abnormal grain growth in Nb-LLZO. The sintering process of the Nb-LLZO/MgO composite ceramics has been studied for different Nb doping levels (0.2–0.7 pfu) at sintering conditions of 1250 °C for 1–360 min. The ceramic density, microstructure, and Li-ion conductivity are reported. The composite ceramics have shown a very fast sintering speed. At 1250 °C, the 0.4Nb-LLZO/MgO composite can be well-sintered in 1 min. For sintering at 1250 °C for 40 min, ceramic samples showing relative density of 97%, conductivity of 6 × 10−4 S cm−1 at 25 °C, and activation energy of 0.40 eV are obtained. [ABSTRACT FROM AUTHOR]