Ceramics-Silikáty 61, (1) 14 - 19 (2017)

The overall conductivity of crystalline lithium ion conductors is generally low due to the large grain boundary resistance. In order to improve the grain boundary conductivity, NASICON structured Li_1+xAl_xSn_2-x(PO₄)₃ has been studied in this paper. Samples Li_1.2Al_0.2Sn_1.8(PO₄)₃ with the desirable amount of Al, made of a mixture of not-treated powders and treated powders in various ratios, are prepared to investigate the mixing effect on the grain boundary conductivity. The grains morphology of samples has changed from spherical shapes to rectangular shapes upon mixing, which indicates a liquid (or glass) phase formation during sintering. The overall conductivity peaks at 20% of not-treated powders. The increase in the overall conductivity is attributed to the increase of grain boundary conductivity, not the grain conductivity. The reason accounting for the enhancement of the grain boundary conductivity is attributed to a less-resistive grain boundary as indicated by the grains morphology changes observed.