Known as a weak topological insulator (TI), BiSe structurally exhibits alternating stacks of quantum spin Hall bilayer (“Bi2”) and three-dimensional TI layer (“Bi2Se3”). The low lattice thermal conductivity of BiSe due to the presence of Bi2 bilayers promises potentially good thermoelectric performance. Herein, the thermoelectric properties of nominal Bi1−xCuxSe samples were studied as the functions of the content of Cu additive and temperature. It is found that Cu additives in BiSe (1) profoundly affect the texture of densified polycrystalline samples by inclining the crystallographic c-axis parallel toward the pressure direction in the densification process, (2) increase considerably the effective mass and thus the Seebeck coefficient, and (3) yield point defects and Cu–Se secondary phases that effectively scatter heat-carrying phonons. As a result, the optimized electrical and thermal properties yield a thermoelectric figure of merit of zT ~ 0.29 in Bi1−xCuxSe (x = 0.03) sample at 467 K in parallel to the pressure direction and a zT ~ 0.20 at 468 K in the perpendicular direction.

中文翻译：

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通过 Cu 添加剂增强有效质量和声子散射优化 BiSe 的热电性能

BiSe 被称为弱拓扑绝缘体 (TI)，在结构上表现出量子自旋霍尔双层 (“Bi2”) 和三维 TI 层 (“Bi2Se3”) 的交替堆叠。由于 Bi2 双层的存在，BiSe 的低晶格热导率有望提供良好的热电性能。在此，研究了标称 Bi1-xCuxSe 样品的热电性能作为 Cu 添加剂含量和温度的函数。发现 BiSe 中的 Cu 添加剂（1）通过在致密化过程中平行于压力方向的晶体学 c 轴倾斜，从而深刻影响致密化多晶样品的织构，（2）显着增加有效质量，从而显着增加塞贝克系数， (3) 屈服点缺陷和有效散射载热声子的 Cu-Se 第二相。