The role of hetero-interface structures in enhancing the power factor of Cu₂Se/x% Y₂O₃ composite thermoelectric materials

In this study, we have investigated the structural, thermal, electrical, and mechanical properties of the composite system Cu₂Se/x% Y₂O₃ (0 ≤ x ≤ 1.00) as a function of varying Y₂O₃ concentration, x. The successful incorporation of Y₂O₃ in the Cu₂Se matrix is carried out using the solid-state reaction method, and the same is confirmed by X-ray diffraction analysis. Due to the low concentration of Y₂O₃, all the prepared composites exhibit monoclinic crystal structure with P2/m space group within the X-ray detection limit at room temperature. The oxidation state of the studied composites is investigated using X-ray photoelectron spectroscopy (XPS). The composites exhibit an increase in mechanical hardness as a function of Y₂O₃ concentration, whereas the electrical resistivity shows no systematic variation with Y₂O₃ concentration. The highest resistivity is observed for the sample with x = 1%. The measured Seebeck coefficient (S) value increases with increasing temperature. The positive values of S indicate that the positive charge carriers (holes) dominate the thermoelectric transport. The thermal conductivity of the composites increases as compared to the Cu₂Se pristine sample. The overall power factor and ZT of studied composites were found to decrease with the addition of Y₂O₃ to the Cu₂Se system.