The effect of sintering on the grain boundary conductivity of lithium lanthanum titanates

The Li-ion conductivity is a sensitive function of the composition and the microstructure for the perovskite-type Li-ion conductor. In this study, the effect of sintering temperature and thus microstructure and Li loss on the grain boundary conductivity of Li-conducting La0.57LixTiO3 (x=0.3 and 0.35) were studied. The grain and the grain boundary conductivity were obtained from the impedance patterns. As the sintering temperature increased from 1100°C to 1350°C, the Li content decreased due to the evaporation of Li during sintering. The samples were nearly fully dense after sintering at 1200°C or above. The grain boundary conductivity increased rapidly with sintering temperature due to the increasing grain size. When the grain conductivity was nearly independent on the sintering condition, the grain boundary conductivity change was mostly explained by the microstructural change. Some possible reasons for the low grain boundary conductivity was discussed.