Synthesis and characterization of Cu2-xTe-type thermoelectric materials

Abstract

The current state-of-the-art p-type thermoelectric material that is widely used in commercial applications is Bi0.5Sb1.5Te3 (BST) and has remained so for the past decades. The highest Figure of Merit, ZT that can be reached for the low temperature thermoelectric material is around 1 at room temperature (300K) which makes it more frequently used in thermoelectric cooling rather than power generation due to its low operating temperature range. Non-stoichiometric copper telluride (Cu2-xTe) was found from literature to be highly degenerate p-type semiconductors that exhibit thermoelectric properties but have very few reported uses in thermoelectric applications. In this work, one-dimensional Cu2-xTe-type nanorods have been effectively synthesized by using Te nanorods as templates due to Tellurium’s inherently anisotropic properties. Through XRD characterization, the value of x in Cu2-xTe nanorods synthesized was found to be 0.25. The synergistic effect of adding highly degenerate Cu1.75Te nanorods at different weight fractions to a relatively less degenerate bulk BST matrix have produced nanocomposites which greatly enhances the Figure of Merit to beyond unity at a higher temperature range. The best enhancement in the Figure of Merit was present in 5 wt% nanocomposite where a high ZT value of 1.8 was obtained around 450K. This value is almost twice the value measured at room temperature for any bulk BST materials currently available. The results are very encouraging and demonstrate that BST with Cu2-xTe-type nanoinclusions not only has the potential of being used in supplementary power generation applications via waste heat harvesting from industrial heat processes, but also has nearly twice the efficiency of the commercial BST being used now at room temperatures.