Effect of sintering process on ionic conductivity of li7-x la3 zr2-x nbx o12 (X = 0, 0.2, 0.4, 0.6) solid electrolytes

Abstract

Garnet-type Li7 La3 Zr2 O12 (LLZO) is considered as a promising solid electrolyte. Nb-doped LLZO ceramics exhibit significantly improved ion conductivity. However, how to prepare the Nbdoped LLZO ceramics in a simple and economical way, meanwhile to investigate the relationship between process conditions and properties in Li7-x La3 Zr2-x Nbx O12 ceramics, is particularly important. In this study, Li7-x La3 Zr2-x Nbx O12 (LLZNx O, x = 0, 0.2, 0.4, 0.6) ceramics were prepared by conventional solid-state reaction. The effect of sintering process on the structure, microstructure, and ionic conductivity of LLZNx O (x = 0, 0.2, 0.4, 0.6) ceramics was investigated. Due to the more contractive Nb-O bonds in LLZNx O ceramics, the cubic structures are much easier to form and stabilize, which could induce the decreased preparation time. High-performance garnet LLZNx O ceramics can be obtained by optimizing the sintering process with lower calcining temperature and shorter holding time. The garnet samples with x = 0.4 calcined at 850◦ C for 10 h and sintered at 1250◦ C for 4 h exhibit the highest ionic conductivity of 3.86 × 10−4 S·cm−1 at room temperature and an activation energy of 0.32 eV, which can be correlated to the highest relative density of 96.1%, and good crystallinity of the grains.