Extremely dense microstructure and enhanced ionic conductivity in hot-isostatic pressing treated cubic garnet-type solid electrolyte of Ga2O3-doped Li7La3Zr2O12

A large number of pores and a low relative density that are frequently observed in solid electrolytes reduce severely their ionic conductivity and thus limit their applicability. Here, we report on the use of hot isostatic pressing (HIP) for ameliorating the garnettype lithium-ion conducting solid electrolyte of Ga2O3-doped Li7La3Zr2O12 (Ga-LLZO) with nominal composition of Li6.55Ga0.15La3Zr2O12. The Ga-LLZO pellets were conventionally sintered at 1075 degrees C for 12 h, and then were followed by HIP treatment at 120MPa and 1160 degrees C under an Ar atmosphere. It is found that the HIP-treated Ga-LLZO shows an extremely dense microstructure and a significantly enhanced ionic conductivity. Coherent with the increase in relative density from 90.5% (untreated) to 97.5% (HIP-treated), the ionic conductivity of the HIP-treated Ga-LLZO reaches as high as 1.13 x 10(-3) S/cm at room temperature (25 degrees C), being two times higher than that of 4.58 x 10(-4) S/cm for the untreated one.