Ionic conductivity and crystal structure for the Li3−2xCr2−xTax(PO4)3 system

The monoclinic phase (P21/n) was formed for 0≤x≤0.6 and the NASICON-type rhombohedral phase (R3̄c) was obtained for the region 0.8≤x≤1.2 in the Li3−2xCr2−xTax(PO4)3 system. The activation energy for Li+ migration was ca. 0.45 eV for the monoclinic structure and ca. 0.36 eV for the rhombohedral structure. The maximum conductivity of 8.4×10−6 S cm−1 at 298 K was obtained for x=0.8 of the Li3−2xCr2−xTax(PO4)3 system. The conductivity of LiCrTa(PO4)3 was enhanced about three to five times by the addition of the lithium salt due to the improvement of the sinterablity. The maximum conductivity was 2.4×10−5 S cm−1 at 298 K for LiCrTa(PO4)3–0.2Li3BO3.