磁控溅射法制备Bi2Te3热电薄膜的研究

Bi2Te3薄膜是室温下热电性能最好的热电材料,利用磁控溅射在长有一薄层SiO2的n型硅样品上制备Bi/Te多层复合薄膜,经后续退火处理生成Bi2Te3。通过分析Bi2Te3薄膜的生长和退火工艺,探讨Bi/Te中Te的原子数分数对薄膜热电性能的影响。采用XRD和SEM对薄膜的结构、形貌和成分进行分析,并测量不同条件下的Seebeck系数。薄膜Seebeck系数均为负数,表明所制备样品是n型半导体薄膜,且最大值达到-76.81μV.K-1;电阻率ρ随Te的原子数分数增大而增大,其趋势先缓慢后迅速。Bi2Te3薄膜的热电性能良好,Te的原子数分数是60.52%时,功率因子最大,为1.765×10-4W.K-2.m-1。     

Bi2Te3热电材料改性研究及其进展

随着全球经济对高效、无污染能源转换的强劲需求,Bi2Te3半导体作为最优异的室温热电材料取得了长足稳步的发展。本文在简述Bi2Te3热电材料的结构和性能的基础上,重点介绍了掺杂、纳米化、掺杂与纳米化相结合的方法对Bi2Te3热电性能的影响,详细分析了其影响机制。结果表明,以上方法均能很大程度上提升Bi2Te3热电材料的热电性能,尤其是掺杂与纳米化相结合对热电性能的提高更为显著。最后,对Bi2Te3热电材料改性的研究方向进行了展望。     

热电材料的研究进展

随着热电材料与薄膜制备技术和性能研究手段的发展,具有高热电性能的热电薄膜和低维结构受到人们关注。目前,国内外研究主要集中在如何提高热电材料的能量转换率等核心技术问题上。介绍了热电材料的理论背景、材料分类、制备手段和热电性质的表征,其中,制备手段及热电性质表征主要以Bi2Te3基热电材料展开论述。最后,对热电材料的发展和未来研究方向进行总结。     

基于Bi_2Te_3合金材料的热发电模块研究

为了提高Bi2Te3热电材料的性能,采用Bi2Te3纳米粉体前驱物快速熔炼烧结法,制备了在室温条件下具有温度敏感性的Bi2Te3合金材料,在425K时此材料的热电优值达到0.548。在此基础上,研制了热电模块,并对其性能进行了测试。结果表明,以该Bi2Te3合金材料制备的热发电模块具有良好的伏安特性和稳定的内阻,当热冷端温度分别为140和60℃时,模块的最大输出功率可达到0.39W,显现出潜在的应用前景。     

电场激活压力辅助烧结对(Bi2Te3)0.2(Sb2Te3)0.8热电材料微观结构及热电性能的影响

采用电场激活压力辅助烧结（FAPAS）技术制备了(Bi2Te3)0.2(Sb2Te3)0.8热电材料,采用无电场、低电场强度和高电场强度三种烧结方式作为对比实验,研究了烧结过程中施加电场强度对(Bi2Te3)0.2(Sb2Te3)0.8热电材料微观结构和热电性能的影响。研究结果表明,在烧结过程中施加电场,可明显提高(Bi2Te3)0.2(Sb2Te3)0.8热电材料的电导率和Seebeck系数,从而提高其综合电功率因子;而采用大电场强度烧结则会使(Bi2Te3)0.2(Sb2Te3)0.8材料出现层状结构择优取向,在电性能相对较高的情况下亦使其热导率明显减低,从而获得较高ZT值。     

制备工艺对新型热电材料制冷性能的影响

通过取点法得到了由Ingot法、BM法、S-MS法和Te-MS法制备的四种新型p型热电材料(Bi0.5Sb1.5)Te3的变物性参数拟合公式,分析了温度对不同方法制备的热电材料的影响,得到了热电材料无量纲优值与绝对温度的关系曲线.从热力学方面研究了制备工艺对基于新型热电材料的热电制冷器最大制冷系数的影响.结果表明:由Te-MS法制备的新型p型热电材料(Bi0.5Sb1.5)Te3具有最大的优值系数,基于该材料的热电制冷器最大制冷系数可达2.49,较其他三种方法制备的热电材料分别提升了 34.59％,37.57％和25.76％.     

Sb2Te3热电薄膜磁控溅射制备工艺

Sb2Te3基半导体合金是目前性能较好的热电半导体材料.将材料低维化处理可以获得较块状材料更大的热电优值.通过磁控溅射工艺制备低维Sb2Te3薄膜,并通过AFM、XRD和XPS测试方法对薄膜的成分、薄膜表面以及原子偏析进行表征.通过退火工艺去除薄膜应力,观察退火工艺前后薄膜表面形貌的变化以及退火温度对薄膜表面质量的影响.试验结果表明通过磁控溅射工艺所制备出的Sb2Te3薄膜为非晶态,随着溅射功率增大,薄膜的表面粗糙度增大.退火可使薄膜变为晶态,但是表面粗糙度增大.较大或较小溅射功率下所制备的薄膜其合金成分与合金靶材有较大偏差.     

(Bi2Te3)0.90(Sb2Te3)0.05(Sb2Se3)0.05热压合金微观结构和电学性能相关性研究

通过熔炼,研磨制备N型(Bi2Te3)0．90(Sb2Te3)0．05(Sb2Se3)0．05热电材料的粉末,热压制备混合粉末热压合金。通过SEM和XRD研究热压合金的微观结构,在室温测量热压合金样品的电学性能。结果表明热压合金在微观结构和电学性能上存在各向异性,从而预示能够在增强材料机械强度的同时提高其热电性能。     

低维Bi_2Te_3热电材料的制备与性能研究

用溶剂热法制备了直径在100nm以内的一维针状及厚20～30nm、长几微米的二维花朵状Bi2Te3热电材料,分析了不同形貌产物的生长机理,并对其热电性能进行了比较。结果表明,添加剂的分子结构对产物形貌起决定性作用。不同形貌产物的热电性能随温度变化的机制不同,一维纳米结构Bi2Te3产物的功率因子随温度升高而增加,最大值为143.1μΩ·m–1K–2。而二维纳米结构的Bi2Te3产物虽然在室温附近有较大的Seebeck系数,约100μV/K,但由于其电导率较低,功率因子在较宽的温度范围内保持在23μΩ·m–1K–2左右。     

脉冲激光沉积法制备Bi2Sr2Co2Oδ热电薄膜及其激光感生的热电电压效应

采用脉冲激光沉积(PLD)法在倾斜Al2O3(0001)衬底上制备了Bi2Sr2Co2Oδ(BSCO)系列热电薄膜,发现该类薄膜中有激光感生热电电压(LITV)效应.X射线衍射(XRD)谱显示Bi2Sr2Co2Oδ热电薄膜沿c轴外延生长.采用标准四探针法测试了Bi2Sr2Co2Oδ热电薄膜的电阻随温度的关系.结果表明所制备的Bi2Sr2Co2Oδ热电薄膜在80～360 K范围内呈半导体导电特性.研究发现,在倾斜角度分别为10°和15°的倾斜衬底上制备的Bi2Sr2Co2Oδ热电薄膜都存在一个最佳厚度,在这一厚度下可使激光感生热电电压(LITV)信号的峰值电压达到最大,分别为0.4442 V和0.7768 V.可以认为该激光感生热电电压信号是由Bi2Sr2Co2Oδ薄膜面内和面间塞贝克系数张量的各向异性引起的.     

Point Defect Engineering of High‐Performance Bismuth‐Telluride‐Based Thermoelectric Materials

Developing high‐performance thermoelectric materials is one of the crucial aspects for direct thermal‐to‐electric energy conversion. Herein, atomic scale point defect engineering is introduced as a new strategy to simultaneously optimize the electrical properties and lattice thermal conductivity of thermoelectric materials, and (Bi,Sb)₂(Te,Se)₃ thermoelectric solid solutions are selected as a paradigm to demonstrate the applicability of this new approach. Intrinsic point defects play an important role in enhancing the thermoelectric properties. Antisite defects and donor‐like effects are engineered in this system by tuning the formation energy of point defects and hot deformation. As a result, a record value of the figure of merit ZT of ≈1.2 at 445 K is obtained for n‐type polycrystalline Bi₂Te_2.3Se_0.7 alloys, and a high ZT value of ≈1.3 at 380 K is achieved for p‐type polycrystalline Bi_0.3Sb_1.7Te₃ alloys, both values being higher than those of commercial zone‐melted ingots. These results demonstrate the promise of point defect engineering as a new strategy to optimize thermoelectric properties.     

The Surface Preparation of Thermoelectric Materials for Deposition of Thin-Film Contact Systems

Semiconductors - The method of mechanical treatment of thermoelectric materials Bi2Te2.8Se0.2 (0.14 wt % of CdCl2), Bi0.5Sb1.5Te3 (2 wt % of Te and 0.14 wt % of TeI4), PbTe (0.2 wt % of PbI2 and...     

Thermoelectric energy converters: Environmental aspects

Semiconductors - The methodological framework for assessing the environmental and economic efficiency of Bi2Te3-based thermoelectric cooling modules is considered taking into account resource...     

Estimation of the band gap of a series of new thermoelectric materials

Semiconductors - The band gap E g of a number of new thermoelectric materials, such as skutterudites, clathrates, Heusler phases, (Ge,Sn,Pb)(Te,Se)] m [(Bi,Sb)2(Te,Se)3] n (m, n = 0, 1, 2…)...     

Thermoelectric Performance Enhancement in BiSbTe Alloy by Microstructure Modulation via Cyclic Spark Plasma Sintering with Liquid Phase

The widespread application of thermoelectric (TE) technology demands high-performance materials, which has stimulated unceasing efforts devoted to the performance enhancement of Bi₂Te₃-based commercialized thermoelectric materials. This study highlights the importance of the synthesis process for high-performance achievement and demonstrates that the enhancement of the thermoelectric performance of (Bi,Sb)₂Te₃ can be achieved by applying cyclic spark plasma sintering to Bi_xSb_2–xTe₃-Te above its eutectic temperature. This facile process results in a unique microstructure characterized by the growth of grains and plentiful nanostructures. The enlarged grains lead to high charge carrier mobility that boosts the power factor. The abundant dislocations originating from the plastic deformation during cyclic liquid phase sintering and the pinning effect by the Sb-rich nano-precipitates result in low lattice thermal conductivity. Therefore, a high ZT value of over 1.46 is achieved, which is 50% higher than conventionally spark-plasma-sintered (Bi,Sb)₂Te₃. The proposed cyclic spark plasma liquid phase sintering process for TE performance enhancement is validated by the representative (Bi,Sb)₂Te₃ thermoelectric alloy and is applicable for other telluride-based materials.