Electrical conductivity and thermoelectric power of La$_{1-x}$Li$_{x}$CоO$_{3-\delta}$ (0 $\le x\le$ 0.1) oxides

The influence of the concentration of lithium ions on the phase composition, the electrical conductivity, and the thermoelectric power of La$_{1-x}$Li$_{x}$CоO$_{3-\delta}$ (0 $\le x\le$ 0.1) oxides synthesized by the ceramic method has been investigated. It has been found that the region of the existence of perovskite-type La$_{1-x}$Li$_{x}$CоO$_{3-\delta}$ solid solutions does not exceed $x$ = 0.05. The doping with lithium leads to an increase in the electrical conductivity of single-phase samples in comparison with that of the LaCoO$_{3}$ compound. As the temperature increases from 300 to 400 K, the thermoelectric power of the LaCoO$_{3}$ compound increases from the negative to positive values and then decreases, but remains positive in the temperature range from 400 to 1020 K. The thermoelectric power of the other samples has a positive sign. The results obtained have been discussed based on the models of the electron density of states in LaCoO$_{3}$ and La$_{1-x}$Sr$_{x}$CоO$_{3-\delta}$, proposed in the studies of Señarís–Rodríguez and Goodenough, as well as in the framework of the theory of non-crystalline materials, developed by Mott.