Synthesis and high-temperature thermoelectric properties of Ni and Ti substituted LaCoO3

The effect of Ti and Ni substitution in LaCoO3-delta was investigated by means of electrical resistivity and Seebeck coefficient properties in a broad temperature range. The studied compounds crystallize in a rhombohedral crystal structure within the whole substitution range. The Seebeck coefficient of most of the studied compounds is positive indicating predominant hole-type charge carriers. The electrical resistivity decreases with increasing temperature for all compositions. Increasing the Ni content results in a decrease of the electrical resistivity, while the resistivity increases with increasing Ti content. The power factor, PF, for the Ni substituted samples is PF = 1.42 x 10(-4) W/m(2) K for x = 0.10 at T = 540 K and decreases with temperature. The LaCo1-xTixO3 +/-delta compounds reveal an enhancement of the power factor with increasing temperature. Ti substitution leads to a higher power factor compared to that of Ni substitution at T = 1240 K. (c) 2006 Elsevier Inc. All rights reserved.