Abstract: Refined natural kaolinite was used as a starting material for preparing new lithium fast ion
conductors of Li_1+2x+yAl_xYb_yTi_2-x-ySi_xP_3-xO₁₂ system by high temperature (950～1150℃) solid phase reaction for about 20h. The syntheses temperatures are lowered with increasing the
value of x and y for the system. The X-ray powder diffraction shows that a Lisicon phase with R3c space group exists in the composition
range of y=0.3, x≤0.4 and y=0.5, x≤0.3. The initial composition with y=0.3, x=0.1 possesses a maximum ionic conductivity of 2.45×10^-2S/cm
at 673K and its activation energy is 38.3kJ/mol in the temperature range of 473～673K.

Key words: Al-Yb-Lisicon, fast ion conductor, kaolinite