Fabrication and properties of thermoelectric oxide thick films deposited with aerosol deposition method

Abstract

Thermoelectric materials can directly convert thermal energy to electric energy via Seebeck effect and have attracted attention for clean energy harvesting material. Ca3Co4O9+δ (Co349) oxide shows a high thermoelectric performance. Since the Co349 is a misfit-layered oxide, the c-axis oriented structure should be required to achieve high thermoelectric performance. In this study, the Co349 thick film was deposited with aerosol deposition (AD) method. The effect of process parameters on the microstructure and thermoelectric properties were investigated. The thermal strain caused by the difference in thermal expansion coefficient should be less than 0.2%. The deposition rate of 2 μm/min could be attained by controlling particle size distribution. The c-axis oriented Co349 film was obtained after the annealing at the temperature higher than 700°C. Seebeck coefficient of 170 (μV/°C) and electrical conductivity of 110 (S/cm) were achieved at 700 °C in the film annealed at 900 °C for 1 hour. The thermoelectric performance could be kept up to the thick film of 55μm. These values were as high as those of the usual bulk samples. This suggests that the AD process is effective to fabricate thick film type thermoelectric module.