Effects of In2O3 nanoparticles addition on microstructures and thermoelectric properties of Ca3Co4O9 compounds

Abstract

The (x) In2O3/(1-x) Ca3Co4O9 (x = 0-15 wt%) composites were prepared using the solid reaction method followed by a spark plasma sintering process. There is no reaction occurring, and the natural c-axis grain-oriented structure is observed in all samples by XRD measurements. Scanning electron microscopy and Energy dispersive spectroscopy observations indicate that the In2O3 nanoparticles are present as the ultrafine particles/clusters secondary phase in Ca3Co4O9. Electric properties measurement shows that the electrical conductivity reduced by adding In2O3 particles, while the seebeck coefficient is virtually unaffected, which leads to the low power factor PF value of Ca3Co4O9. Significantly, however, there is an obvious recovery in the electrical conductivity of S15 sample compared to that of S5 and S10 samples, which also results in a rise again in PF of S15. This result may be of significance for further increase In2O3 secondary phase content (x > 15 wt%) to enhance the thermoelectric property of Ca3Co4O9.