Improving the thermoelectric properties of Ca3Co4O9 by reducing thermal conductivity through composite nano-ZnO

Abstract

Composite nanomaterial is a scientific solution to modulating the properties of thermoelectric materials. The thermoelectric properties of Ca₃Co₄O₉ ceramic that remain stable in high-temperature air are relatively low, and how to decouple the relationship between heat and electricity is the focus of the research. This study systematically investigates the thermoelectric transport properties of composite Ca₃Co₄O₉@xZnO materials. The samples do not undergo additional chemical reactions and exhibit lamellar microstructures. At temperatures up to 825 K, the thermal conductivity of pure Ca₃Co₄O₉ was determined to be 2.58 W m⁻¹ K⁻¹, whereas that of the Ca₃Co₄O₉@0.7ZnO was significantly reduced to 1.94 W m⁻¹ K⁻¹, a reduction of about 25%. Based on the effective medium theory analysis, adding ZnO in Ca₃Co₄O₉ introduces interfacial thermal resistance and porosity, which is key in reducing thermal conductivity. Adding ZnO promotes the electrical conductivity enhancement of Ca₃Co₄O₉ with a minor reduction in the Seebeck coefficient. Under the coordinated regulation of electrical and thermal properties, the ZT of Ca₃Co₄O₉@0.7ZnO is enhanced by about 75% compared with that of pure Ca₃Co₄O₉.