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

The effect of Ti and Ni substitution in LaCoO3−δ 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=1.42×10−4 W/m2 K for x=0.10x=0.10 at T=540K and decreases with temperature. The LaCo1−xTixO3±δ   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=1240K.

Graphical abstractThe three parameters defining the thermoelectric figure of merit are interdependent. As e.g. the thermopower increases so does the resistivity. Therefore, an optimum charge carrier concentration and mobility has to be defined in rhombohedral thermoelectric cobaltate structures. The heat conductivity can be lowered by enhanced boundary scattering in nanostructured materials without changing the electronic transport.Figure optionsDownload full-size imageDownload as PowerPoint slide