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Bi2Te3基化合物是目前唯一实现商业化应用的热电材料，但对其研究大多都集中于室温及以上温区，针对室温以下的低温区研究较少。本工作系统地研究了Bi/Sb相对含量调控和Se固溶对BixSb2-xTe3和Bi0.4Sb1.6Te3-ySey化合物在低温区电热输运性能的影响规律。在BixSb2-xTe3体系中，固溶Bi2Te3减小了材料的带隙，并降低了SbTe反位缺陷的浓度，使材料的峰值ZT温度向低温区偏移，但显著增强的载流子点缺陷散射，导致材料的载流子迁移率和电传输性能劣化，功率因子从Bi0.4Sb1.6Te3的4.58 mW/(m·K2)下降至Bi0.58Sb1.42Te3的1.12 mW/(m·K2)。为了进一步提升材料低温区热电性能，选取Bi0.4Sb1.6Te3为基体，在Te位固溶Se，Se的固溶使SeTe+BiSb的缺陷形成能更低，抑制了反位缺陷SbTe的产生，降低了材料的载流子浓度。少量Se固溶使材料能保持优异的电传输性能同时，显著增强了点缺陷声子散射，降低材料的晶格热导率，在宽温区范围提升了材料的热电性能。Bi0.4Sb1.6Te3材料在220 K时，ZT值为0.80，在350 K时ZT峰值为1.17，少量Se固溶Bi0.4Sb1.6Te2.97Se0.03样品在220 K时ZT值增加至0.93。在350 K时ZT峰值达到1.31，相比分别提升了约16%和12%。该研究为BiSbTe基热电材料低温区热电性能提升提供了重要的指导，对BiSbTe基热电材料低温区的应用具有重要意义。
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关键词:
- Bi2Te3基化合物 /
- 低温热电性能 /
- 能带工程 /
- 缺陷工程
Bi2Te3-based compounds are the only commercially available thermoelectric materials, yet their low-temperature performance below 300 K remains underdeveloped. This study systematically explores the effects of Bi/Sb ratio modulation and Se substitution on the electrical and thermal transport properties of BixSb2-xTe3 and Bi0.4Sb1.6Te3-ySey materials. The research aims to optimize their thermoelectric performance in cryogenic regions through combined bandgap tuning and defect engineering. Materials were synthesized using a melt-quenching and spark plasma sintering process, followed by phase analysis via X-ray diffraction and microstructural characterization by electron probe microanalysis. First-principles calculations and Hall effect measurements were employed to investigate defect formation mechanisms and carrier transport behavior. In the BixSb2-xTe3 system, increasing Bi content reduced the bandgap from 0.168 eV for Bi0.4Sb1.6Te3 to 0.113 eV for Bi0.58Sb1.42Te3, shifting the peak ZT temperature to lower ranges. However, enhanced alloy scattering degraded carrier mobility from 332 to 109 cm2/(V·s) and power factor from 4.58 to 1.12 mW/(m·K2). To address this, Se was substituted into the Te lattice of Bi0.4Sb1.6Te3. First-principles calculations revealed that Se substitution reduced the formation energy of SeTe + BiSb complexes, effectively suppressing SbTe antisite defects. This resulted in a carrier concentration decrease from 3.32×1019 to 2.64×1019 cm-3 while maintaining high mobility at 279 cm2/(V·s). Concurrently, Se-induced point defects enhanced phonon scattering, lowering lattice thermal conductivity by 17 % from 0.46 to 0.38 W/(m·K). Bi0.4Sb1.6Te2.97Se0.03 sample achieved a ZT value of 0.93 at 220 K, representing a 16 % improvement over the pristine Bi0.4Sb1.6Te3 sample with a ZT value of 0.80. The peak ZT increased from 1.17 to 1.31 at 350 K, demonstrating a 12 % enhancement. These improvements arise from the synergistic effects of band engineering, where flattened valence band edges increased effective mass, and defect engineering, which suppressed antisite defects and strengthened phonon scattering. This work provides a dual optimization strategy for BiSbTe-based materials, balancing bandgap reduction with defect control to improve cryogenic performance. The findings are particularly relevant for applications in infrared detectors and multistage thermoelectric cooling systems.-
Keywords:
- Bi2Te3-based compounds /
- low-temperature thermoelectric properties /
- band engineering /
- defect engineering
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