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

Composite nanomaterial is a scientific solution to modulating the properties of thermoelectric materials. The thermoelectric properties of CaCoO 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 CaCoO@ZnO materials. The samples do not undergo additional chemical reactions and exhibit lamellar microstructures. At temperatures up to 825 K, the thermal conductivity of pure CaCoO was determined to be 2.58 W m K, whereas that of the CaCoO@0.7ZnO was significantly reduced to 1.94 W m K, a reduction of about 25%. Based on the effective medium theory analysis, adding ZnO in CaCoO introduces interfacial thermal resistance and porosity, which is key in reducing thermal conductivity. Adding ZnO promotes the electrical conductivity enhancement of CaCoO with a minor reduction in the Seebeck coefficient. Under the coordinated regulation of electrical and thermal properties, the of CaCoO@0.7ZnO is enhanced by about 75% compared with that of pure CaCoO.