Thermoelectric Property Studies on Cu‐Doped n‐type Cu_xBi₂Te_2.7Se_0.3 Nanocomposites

Abstract Combining high energy ball‐milling and hot‐pressing, significant enhancements of the thermoelectric figure‐of‐merit ( ZT ) have been reported for p‐type Bi 0.4 Sb 1.6 Te 3 nanocomposites. However, applying the same technique to n‐type Bi 2 Te 2.7 Se 0.3 showed no improvement on ZT values, due to the anisotropic nature of the thermoelectric properties of n‐type Bi 2 Te 2.7 Se 0.3 . Even though texturing was effective in improving peak ZT of Bi 2 Te 2.7 Se 0.3 from 0.85 to 1.04, reproducibility from batch to batch remains unsatisfactory. Here, we show that good reproducibility can be achieved by introducing an optimal concentration of 0.01 copper (Cu) per Bi 2 Te 2.7 Se 0.3 to make Cu 0.01 Bi 2 Te 2.7 Se 0.3 samples. A peak ZT value of 0.99 was achieved in Cu 0.01 Bi 2 Te 2.7 Se 0.3 samples without texturing. With texturing by re‐pressing, the peak ZT was increased to 1.06. Aging in air for over 5 months did not deteriorate but further improved the peak ZT to 1.10. The mechanism by which copper improves the reproducibility, enhances the carrier mobility, and reduces the lattice thermal conductivity is also discussed.