The impact of Yb substitution on enhancing the thermoelectric properties of CuMnO2 nanostructures

In the present work, CuMn1-xYbxO2 nanostructure with various x values (x ​= ​0, 0.05, 0.1, 0.2) were prepared by high energy ball milling. The structural and morphological properties of the prepared samples were studied by XRD and SEM, analyses. XRD analysis confirms that a pure phase of copper manganese oxide (CuMnO2) was formed till x ​= ​0.05 and the secondary phase of Yb2O3 was observed while increasing the Yb concentration (x ​≥ ​0.1). The SEM images show nano rod-like morphology till x ​= ​0.1 and nanorods were agglomerated in the samples with higher values (x ​> ​0.1). The electrical resistivity and Seebeck coefficient of CuMn1-xYbxO2 (0 ≤ x ​≤ ​0.2) samples were measured at various temperatures. The electrical resistivity of the samples decreased till x ​≤ ​0.1 due to the complete dissolution of Yb ions in CuMnO2 lattice and the resistivity increases at higher Yb substitution (x ​> ​0.2) due to the secondary phase of Yb2O3. The Seebeck coefficient value decreased at x ​= ​0.1 and it increases at a higher x value of 0.2. CuMn0.09Yb0.05O2 shows a higher power factor of 0.0013 ​mW. K−2 m−1 at 575 ​K and low thermal conductivity of 3.2 ​W/m K at 668 ​K which are higher than pure samples. The experimental results show that Yb substitution has an enhanced effect on improving the thermoelectric properties of CuMnO2 nanostructure. The result reveals that the 0.05 ​Yb substituted sample shows a higher figure of merit (ZT) of 2.5x10−4 at 668 ​K. Yb substitution at Mn site significantly increased the power factor and reduced the thermal conductivity of CuMnO2 nanostructures which enhanced the figure of merit. [Display omitted] •CuMn1-xYbxO2 (0 ≤ x ​≤ ​0.2) nanostructures were prepared by ball milling method.•The electrical resistivity decreased till x ​≤ ​0.1 due to the complete dissolution of Yb in CuMnO2.•The Seebeck coefficient decreased till x ​= ​0.1 and increased at a higher x value of 0.2.•CuMn0.09Yb0.05O2 shows a higher power factor of 1.3 ​μW K−2cm−1at 648 ​K.•High power factor and low thermal conductivity of CuMn0.09Yb0.05O2 enhanced the ZT.