Bi_2Te_3 has been recognized as an important cooling material for thermoelectric applications. Yet its thermoelectric performance could still be improved. Here we propose a band engineering strategy by optimizing the converging valence bands of Bi_2Te_3 and Sb_2Te_3 in the (Bi_(1−x)Sb_x)_2Te_3 system when x = 0.75. Band convergence successfully explains the sharp increase in density-of-states effective mass yet relatively constant mobility and optical band gap measurement. This band convergence picture guides the carrier concentration tuning for optimum thermoelectric performance. To synthesize homogeneous textured and optimally doped (Bi0.25Sb0.75)2Te3, excess Te was chosen as the dopant. Uniform control of the optimized thermoelectric composition was achieved by zone-melting which utilizes separate solidus and liquidus compositions to obtain zT = 1.05 (at 300 K) without nanostructuring.

中文翻译：

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(Bi 0.25 Sb 0.75 ) 2 Te 3 由于能带收敛和通过载流子浓度控制而提高的高热电性能

Bi_2Te_3 已被公认为热电应用的重要冷却材料。然而，其热电性能仍有待提高。在这里，我们通过优化 (Bi_(1−x)Sb_x)_2Te_3 系统中 Bi_2Te_3 和 Sb_2Te_3 的收敛价带，当 x = 0.75 时提出了一种能带工程策略。能带收敛成功地解释了态密度有效质量急剧增加但迁移率和光学带隙测量相对恒定的原因。该波段会聚图指导载流子浓度调整以获得最佳热电性能。为了合成均匀织构和最佳掺杂的 (Bi0.25Sb0.75)2Te3，选择过量的 Te 作为掺杂剂。