Sn掺杂对p型BiSbTe合金热电性能的影响

采用高能球磨制粉、直流热压成型的方法制备Sn掺杂Bi_0.5Sb_1.5Te₃合金的块材试样(Bi_0.5Sb_1.5)_1-xSn_xTe₃ (x=0, 0.25%, 0.5%, 1%), 对试样的物相、微观结构和热电性能进行分析。X线衍射图谱表明所有样品的物相均为Bi_0.5Sb_1.5Te₃, Sn掺杂后没有出现第二相。扫描电镜图像表明Sn掺杂对晶粒尺寸的影响不大, 因而晶格热导率变化不大。通过Sn的掺杂, 试样在提高电导率的同时降低了塞贝克系数, 这主要是由于Sn掺杂对载流子浓度的影响。试样Bi_0.5Sb_1.5Te₃的量纲一热电优值ZT在348 K达到1.16, 在423 K之前均大于1, 比传统方法制备的BiSbTe合金的ZT平均值提高了20%, 这有利于热电的实际应用。

Effects of Sn Doping on Thermoelectric Properties of p Type BiSbTe Alloy

A series of Sn-doped (Bi_0.5Sb_1.5)_1-xSn_xTe₃ (x=0, 0.25%, 0.5%, 1%) bulk samples were prepared by nano powders from high-energy ball milling and compacted samples from direct current pressing method.Then the phase, microstructure and thermoelectric properties of the samples were analyzed.The X-ray diffraction patterns showed that there was no other phases except Bi_0.5Sb_1.5Te₃ in all bulk samples, while the Scanning Electron Microscope images indicated that Sn doped samples had little effect on the grain size, resulting little change in lattice thermal conductivity.The Sn doped samples got higher Seebeck coefficient and lower electrical conductivity, which was mainly because of the influences on the carrier density from Sn dopant.The maximum dimensionless figure of merit ZT of 1.16 was archived at 348 K in Bi_0.5Sb_1.5Te₃ sample, which was mainly attributed to the reduced lattice thermal conductivity from the enhanced phonon scattering by the interfaces of greatly increased micron or sub-micron grains and precipitation than the sample prepared by conventional method.The prepared Bi_0.5Sb_1.5Te₃ sample's ZT is higher than 1 before 423 K, about 20% improving comparing with the average ZT of the sample prepared by traditional method, which is advantageous for practical application.