Enhancement of thermoelectric properties in CuI-doped Bi₂Te_2.7Se_0.3 by hot-deformation

We investigated the thermoelectric properties of CuI-doped Bi₂Te_2.7Se_0.3 compounds, fabricated by a repetitive hot-deformation process. The degree of texture of the materials was enhanced by the number of hot-deformation processings, and experimentally verified by X-ray diffraction measurements. Very interestingly, the enhanced texture induced by the hot-deformation produced a moderate reduction in electrical resistivity by improving electron mobility, while the Seebeck coefficient remained almost unchanged. The corresponding power factor at room temperature was significantly improved, from 3.1 mW m⁻¹ K⁻² to 4.1 mW m⁻¹ K⁻² after two successive hot-deformation processings, and consequently a high value of ZT of 1.07 was achieved at 423 K. This demonstrates that tuning the texture of Bi₂Te₃ based materials by multiple hot-deformation processing steps can be an effective approach for increasing ZT.