Substitution effect on the thermoelectric properties of reduced Nb-doped Sr0.95La0.05TiO3 ceramics

Ceramic samples of Sr0.95La0.05Ti1-xNbxO3 (0 <= x <= 0.10) have been prepared by the solid-state reaction method. From their crystal structures determined by means of the powder X-ray diffraction, we found that the lattice parameters increase with increasing niobium content. The electrical resistivity. Seebeck coefficient and thermal conductivity have been measured in the temperature range between 300 K and 1100 K. All samples show large negative Seebeck coefficient, which is indicative of a n-type conduction. The high-temperature electrical resistivity and the absolute Seebeck coefficients decrease with the increase of niobium content. The electrical resistivity decreases from 10.3 m Omega cm for x = 0 at 1043 K to 5.4 m Omega cm for x = 0.10 at 1042 K. The thermal conductivity decreases with increasing temperature for all samples, and shows no distinct influence by the niobium substitution. The power factor is decreased in niobium doping samples, as there is no effectively decreasing of the electrical resistivity but reduction of Seebeck coefficient. Therefore, the highest thermoelectric figure of merit still observed in Sr0.95La0.05TiO3, reaches 0.21 at 973 K, which is 40% larger than that of the stoichiometric single crystal. (C) 2009 Elsevier B.V. All rights reserved.