Effects of additions of carbon nanotubes on the thermoelectric properties of Ni0.05Mo3Sb5.4Te1.6

•Various composites of Ni0.05Mo3Sb5.4Te1.6 with carbon nanotubes were synthesized and characterized.•In each case, the thermoelectric figure-of-merit increases rapidly with increasing temperature.•With increasing amount of carbon nanotubes, the thermal conductivity decreases more than the electrical conductivity.•The composite with 3% carbon nanotubes performs better than the bulk material by 25%.

To prepare Ni0.05Mo3Sb5.4Te1.6, the starting materials were loaded in the stoichiometric ratio into silica tubes and then heated at 1000 K. The reaction products were mixed and divided into four equal parts. The first sample was used as a reference sample called bulk. For the remaining samples, 1%, 2% and 3% by mass of MWCNT (multi-wall carbon nanotubes) were added by ball-milling. These materials were then subjected to consolidation by hot-pressing at 850 K and 56 MPa. Their transport properties were determined and compared to study the influence of MWCNT on the transport properties of Ni0.05Mo3Sb5.4Te1.6. Scanning and transmission electron microscopy were used to study the microstructural and nanostructural features of the samples, and Raman characterization was performed to look for changes induced by ball-milling and hot-pressing of the nanotubes. Mainly due to a largely reduced thermal conductivity by 40% and a slightly reduced power factor, the figure-of-merit was improved by 25% after addition of 3 mass% of MWCNT.

Graphical abstractFigure-of-merit of various Ni0.05Mo3Sb5.4Te1.6/CNT composites. Figure optionsDownload full-size imageDownload as PowerPoint slide