Effect of Ni substitution on electrical and thermoelectric properties of LaCoO3 ceramics

LaCo1-xNixO3 (0 <= x <= 0.2) ceramics were prepared by solid state reaction and their thermoelectric properties were investigated from room temperature (RI) to 400 degrees C. In the range from RT to 180 degrees C, LaCoO3 showed a large negative Seebeck coefficient, but it changed to a positive value above 180 degrees C. However, the Seebeck coefficient became positive in the whole investigated temperature span due to Ni substitution for Co even for a tiny amount, but its absolute value decreased significantly with increasing Ni content. The LaCo0.9Ni0.1O3 composition showed an enhanced power factor with a maximum value of 1.41 x 10(-4) W m(-1) K-2 at room temperature, which is about 3.5 times higher than that of un-doped LaCoO3. Because the power factor decreased and the thermal conductivity increased apparently with temperature, the ZT values were not increased at elevated temperatures, in spite of a relatively large ZT value of 0.031 at a low temperature (50 degrees C) obtained in the composition LaCo0.9Ni0.1O3. (C) 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved.