THE ELECTRICAL-PROPERTIES OF CERAMIC ELECTROLYTES FOR LIMXTI2-X(PO4)3+YLI2O, M = GE, SN, HF, AND ZR SYSTEMS

The electrical properties of systems of LiMxTi2-x(PO4)3+yLi2O, M = Ge, Sn, Hf, and Zr, were examined in detail. The conductivity and the sinterability increased with the amount of excess lithium oxide in the phosphate. The secondary Li2O phase acts as a flux to accelerate the sintering process and to obtain high conductivity grain boundaries. The conductivity decreased and the activation energy of the bulk component for Li+ migration increased by the partial substitution of Ti4+ for M4+ in systems of LiMxTi2-x(PO4)3+0.2Li2O, M = Ge, Sn, Hf, and Zr. A minimum activation energy of 0.28-0.30 eV, was obtained for the sample with ca. 1310 angstrom3 in the cell volume. LiTi2(PO4)3 has the most suitable tunnel size for a Li+ migration through the NASICON-type network structure.