Fabrication and thermoelectric properties of CuMn1+xO2 (x=0~0.2) ceramics

Abstract Crednerite CuMnO 2 ceramic has been investigated for the first time in this study as a potential thermoelectric material based on its low band gap and layer structure. Undoped CuMn 1+ x O 2 (0≤ x ≤0.2) samples with a delafossite structure were prepared via solid-state reactions and sintered at 1353 K for 2.5 h in argon. The phase, microstructure, and thermoelectric properties of the CuMn 1+ x O 2 (0≤ x ≤0.2) samples were discussed by adjusting the sample composition. The crystallinity and microstructure of sintered bulks were analyzed using X-ray diffraction and scanning electron microscopy, respectively. The thermoelectric properties of the samples were studied from room temperature to 573 K. CuMn 1+ x O 2 sintered bulks showed a relative density of 91% and a layered structure. The composition affected the phases and thermoelectric properties of sintered bulks. Bulks with the crednerite CuMnO 2 phase were only obtained at x =0.1 or 0.143. The crednerite CuMn 1+ x O 2 (0≤ x ≤0.2) samples were p-type semiconductors. The Seebeck coefficient ( S ) increased and the electrical conductivity ( σ ) decreased with Mn content up to x =0.1. Excess Mn content ( x >0.143) decreased the Seebeck coefficient and increased electrical conductivity. The power factor (PF) of the CuMn 1+ x O 2 (0≤ x ≤0.2) samples improved due to the significant increase in the Seebeck coefficient. The thermal conductivity ( κ ) decreased with increasing temperature. The lowest κ value (6.79 W m −1 K −1 ) was found for the CuMn 1.1 O 2 sample at 573 K. The dimensionless figure of merit ZT values of the undoped CuMn 1+ x O 2 bulks are too small for these bulks to be candidates for thermoelectric materials due to weak electrical conductivity.