Structural and thermoelectric characterization of Ba substituted LaCoO3 perovskite-type materials obtained by polymerized gel combustion method

Structural and thermoelectric transport properties of Ba2+ containing lanthanum cobaltate (La1−xBaxCoO3; x = 0.01, 0.03, 0.05) prepared by soft chemistry method were investigated and discussed. The influence of the fuel-to-oxidizer ratio (Φ) of the redox mixture on the powder microstructure was studied. The agglomeration grade of the nanocrystalline perovskite phases can be influenced due to initial composition of the redox mixture. Since the different burning characteristic of the polymerized gels results in different xerogel structures, the as-calcined single phase perovskite samples show different compacting and sintering behavior. The thermoelectric transport properties were measured in the 300-1300 K temperature range. It was found that the electrical and thermal conductivity of the sintered pellets show strong dependence on microstructure. In addition increasing Ba2+ content in the samples results in lower thermal conductivity values (κ < 1.5 W/K m). The calculated dimensionless figure of merit (ZT) showed maximum value in the 400-500 K range.