N型Bi_(2)Te_(2.7-z)S_(z)Se_(0.3)热电材料的微观组织与热电性能

The microstructure and thermoelectric properties ofn-type Bi_(2)Te_(2.7-z)S_(z)Se_(0.3) thermoelectric material

通过真空熔炼、快速凝固、球磨制粉、冷压成形和常压烧结工艺,制备了Bi_(2)Te_(2.7-z)S_(z)Se_(0.3)热电材料,表征了Bi_(2)Te_(2.7-z)S_(z)Se_(0.3)热电材料晶体结构、微观形貌、塞贝克系数、热导率、热电优值和功率因子等热电性能。研究了掺杂S的Bi_(2)Te_(2.7-z)S_(z)Se_(0.3)热电材料热电性能与机理。结果表明,Bi_(2)Te_(2.7-z)S_(z)Se_(0.3)热电材料晶体结构为R-3m空间群斜方晶系的六面体层状结构;掺杂S的Bi_(2)Te_(2.7-z)S_(z)Se_(0.3)热电材料,生成较Bi-Te化学键强的Bi-S,V¨Te空位形成能E_(v)(Bi-Te)降低,Bi′Te位缺陷形成能E AS(Bi-Te)增加,抑制反位缺陷Bi′Te,降低了格热导率和双极扩散热导率。同时使Bi_(2)Te_(2.7)Se_(0.3)热电费米能级向导带移动,能带间隙增大,提高本征激发温度,减少少数载流子浓度,态密度(DOS)有效质量增大,塞贝克系数和功率因子增大。300~400 K,Bi_(2)Te_(2.62)S_(0.08)Se_(0.3)热电材料的塞贝克系数约:-224μV/K,热电优值(ZT)约:0.85,功率因子约:1.48 mW/(m·K 2),对开发低温制冷和温差发电材料具有一定实际意义。

In this experiment,Bi_(2)Te_(2.7-z)S_(z)Se_(0.3) thermoelectric materials have been prepared by vacuum melting,rapid solidification method,ball milling,cold pressing and atmospheric sintering.The thermoelectric properties of Bi_(2)Te_(2.7-z)S_(z)Se_(0.3) thermoelectric material such as crystal structure,micro morphology,Seebeck coefficient,thermal conductivity,thermoelectric figure of merit,and power factor were characterized.The thermoelectric performance mechanism of S-doped Bi_(2)Te_(2.7-z)S_(z)Se_(0.3) thermoelectric material was studied.The result shows that the crystal structure of Bi_(2)Te_(2.7-z)S_(z)Se_(0.3)thermoelectric material is a hexahedral layered structure of R-3m space group orthorhombic system.The Bi_(2)Te_(2.7-z)S_(z)Se_(0.3) thermoelectric material doped with S produces a strong chemical bond of Bi-S than Bi-Te chemical bond.The V′Te vacancy formation energy E_(v)(Bi-Te)is reduced,and the Bi′Te anti-site defect formation energy E AS(Bi-Te)is increased,suppressing the inversion defect Bi′Te and reducing the lattice thermal conductivity and bipolar diffusion thermal conductivity.At the same time,the Bi_(2)Te_(2.7)Se_(0.3) thermoelectric Fermi energy level is moved to the guide band.The energy band gap is increased,the intrinsic excitation temperature is increased,the minority carrier concentration is reduced,the effective mass of DOS is increased,and the Seebeck coefficient and power factor are increased.Its thermal conductivity is about 300-400 K,Seebeck coefficient of Bi_(2)Te_(2.62)S_(0.08)Se_(0.3) thermoelectric material is about-224μV/K,ZT value is about 0.85,power factor is about 1.48 mW/(m·K 2).It shows practical application value for low temperature range refrigeration and temperature difference power generation.