Phase Content and Conductivity of Aluminum- and Tantalum-Doped Garnet-Type Lithium Lanthanum Zirconate Solid Electrolyte Materials

摘要

Cubic garnet-type Li_7La_3Zr_2O_(12) (LLZO) was prepared by co-precipitation method. X-ray diffraction results showed that aluminum additions of 0.2 - 0.3 mol% or a tantalum addition with a 0.25 mol% with excess 10% LiOH added in the final sintering step, led to the formation of the cubic LLZO phase. Samples have a low relative density of ～80%, which is the main reason for low ionic conductivity. The total conductivity at 25°C and activation energies of Li_(6.28)La_3Zr_2Al_(0.24)O_(12) and Li_(6.28)La_3Zr_(1.75)Ta_(0.25)O_(12) were 2.8 × 10~(-6) S/cm (0.39 eV for bulk and 0.33 eV for grain boundary) and 7.0 × 10~(-6) S/cm (0.065 eV at low temperature and 0.99 eV at high temperature), respectively.