Facile synthesis of Cu7Te4 nanorods and the enhanced thermoelectric properties of Cu7Te4–Bi0.4Sb1.6Te3 nanocomposites

Nanocomposite thermoelectric (TE) materials have received great interest in recent years due to the large improvement in the figure of merit (ZT), which exceed the ZT≈1 barrier. Herein, we report a facile method for the synthesis of surfactant-free Cu7Te4 using Te nanorods as templates, and the observed improvement of TE properties obtained by dispersing Cu7Te4 nanorods in a Bi0.4Sb1.6Te3 matrix. The matrix itself yields a maximum power factor of 2.45 mW/m K2 at 300 K, while the addition of 5 wt% of Cu7Te4 nanorods increases and shifts the maximum power factor to 3.3 mW/m K2 at 345 K. The maximum ZT obtained for the 5 wt% Cu7Te4–Bi0.4Sb1.6Te3 nanocomposite is 1.14 at 444 K, which is nearly 27% higher than the peak ZT achieved for the Bi0.4Sb1.6Te3 matrix.

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► Simple and highly scalable synthesis of surfactant-free copper telluride nanorods.
► Improved electrical conductivity in nanocomposites with copper telluride addition.
► Maximum power factor shifted from 2.45 mW/m K2 at 300 K to 3.3 mW/m K2 at 345 K.
► Best ZT of 1.14 achieved is 27% higher than peak ZT of bulk.
► ZT>1 obtained over a large temperature range 360–500  K.