Influence of the order of fabrication sequences on the thermoelectric properties of skutterudite CoSb3-Cu0.6Ni0.4 nanocomposites

Nanocomposite samples of CoSb3-xCu(0.6)Ni(0.4) (x = 1, 3.5, 6, and 9 wt%) were fabricated through two different approaches to understand the influence of fabrication processes on the thermoelectric properties of CoSb3 skutterudite. CoSb3 matrix and Cu0.6Ni0.4 nanoalloy were synthesized separately via hydrothermal procedures. The mixtures of as-hydrothermally synthesized powders were prepared and annealed in the first method, while in the second fabrication route, CoSb3 powders were initially annealed, followed by mixing with Cu(0.6)Ni(0.4 )and annealing of the composite at the same conditions. The results showed improved electrical conductivity of CoSb3 compounds, which is consistent with the systematic increase of the carrier concentration upon increasing the Cu(0.6)Ni(0.4 )content. The grain boundary potential barrier mechanism was used to describe the influence of Cu0.6Ni0.4 nanoalloy on the height of the energy barrier of CoSb3 -xCu(0.6)Ni(0.4), as compared with that of pristine CoSb3 synthesized using the similar hydrothermal method. The onset of bipolar thermopower reduction is shifted to higher temperatures; however, the room temperature thermopower is reduced upon increasing the content of Cu0.6Ni0.4 nanoinclusions. The sample containing 1 wt% of Cu0.6Ni0.4 fabricated through the first fabrication procedure showed the highest zT value at similar to 550 K. (C) 2020 Elsevier B.V. All rights reserved.