Thermoelectric properties of LaNi1−xCoxO3 solid solution

We present the results of a systematic investigation of the thermal conductivity, Seebeck coefficient and electrical resistivity for selected members (x=0.3, 0.7, 0.8, and 1) of the LaNi1−xCoxO3 solid solution in the temperature range of 80⩽T⩽320 K. Substitution of Ni by Co drives the system from n-type metallic phase with low thermopower values into p-type semiconducting phase with high thermopower values of the order of hundreds of μV/K. But the thermal conductivity observed varies only slightly with the composition, x, over the temperature range investigated. The latter effect also holds true for the lightly hole doped x=0.8 member (in substituting Sr for La). Our results suggest that semiconducting members of the LaNi1−xCoxO3 solid solution can be classified as “phonon glass and electron crystal” systems. The highest room temperature figure of merit was exhibited by the x=0.8 member (ZT=0.022), which is comparable to that of single crystal NaCo2O4 (ZT=0.03).