IONIC-CONDUCTIVITY OF LI+ ION CONDUCTORS, LI4.2MXSI1-XO4 (M = B-3+, AL-3+, GA-3+, CR-3+, FE-3+, CO-2+, NI-2+)

Ionic conductivities of lithium ion conductors, Li4.2MxSi1-xO4, with the trivalent ions. B3+, Al3+, Ga3+, Cr3+, Fe3+, and disvalent ions, Co2+, Ni2+ are discussed in the view of crystal chemistry. The highest conductivity of σ=1.58×10-3 S cm-1 at 300°C was observed in the Al3+ substituted compound. This value is larger by two orders of magnitude than that of Li4SiO4. Refinement of the cell constants for each compound showed that the volume expansion would be attributed to the extra lithium ion content (x=0.2) and MO4 tetrahedron expansion. This may cause the high ionic conductivity, possibly due to the increase of charge carrier concentration. © 1990.