Low-temperature sintering and enhanced thermoelectric properties of LaCoO ₃ ceramics with B ₂O ₃-CuO addition

LaCoO ₃ ceramics with much enhanced thermoelectric properties were prepared by means of a polyacrylamide gel soft-chemical method and the addition of the sintering aids mixture of B ₂O ₃ and CuO. The effects of B ₂O ₃-CuO addition on the low-temperature sintering behavior, microstructure and thermoelectric properties of LaCoO ₃ ceramics were investigated. The results showed that the sintering temperature of LaCoO ₃ ceramics could be reduced significantly from 1200 °C to 1000 °C by using B ₂O ₃-CuO additions. Although the Seebeck coefficient S of LaCoO ₃ at a temperature below 200 °C decreased with the increase of B ₂O ₃-CuO content x (wt.%), the electric conductivity and thermal resistivity were simultaneously enhanced with increasing x as x ≤ 2.5. Thus, the power factor P of LaCoO ₃ increased with x, and the sample with x = 2.5 sintered at 1000 °C was found to have optimum thermoelectric properties with ZT = 0.073 at 100 °C, which was about 1.5 times higher than that of pure LaCoO ₃ sintered at 1200 °C, indicating that the addition of B ₂O ₃-CuO could simultaneously lower the sintering temperature and improve the thermoelectric properties of LaCoO ₃ ceramics.