In order to improve the thermoelectric properties, hot-pressing sintering and ultra high pressure sintering methods wereadopted to fabricate BiSbx. The phase and crystal structures were determined by X-ray diffraction analysis (XRD). The thermoelectricproperties were measured at 303 K along the direction parallel to the pressing direction. The electric conductivity of the samples wasmeasured at 303 K by the four-probe technique. To measure the Seebeck coefficient, heat was applied to the samples placed betweentwo Cu discs. The thermoelectric electromotive force (E) was measured upon applying small temperature differences ( △T＜2℃)between the both ends of the samples. The Seebeck coefficient of the samples was determined from the value of E/△T. The resultsindicate that the thermoelectric properties of the samples fabricated by UHPS (ultra high pressure sintering) method are much higherthan that by HPS (hot pressing sintering) method and have the highest values at x=0.7.
Guiying Xu, Zhangjian Zhou, Sitong Niu, and Jianqiang LiuLaboratory of Special Ceramics and Powder Metallurgy, University of Science and Technology Beijing, Beijing 100083, China
The p-type (Bi0.15Sb0.85)2Te3 and PbTe are typical thermoelectric materials used for low and middle temperature range and functional graded materials (FGM) is an inevitable way to widen the working temperature range. Here two segments graded thermoelectric materials (GTM) consisting of (Bi0.15Sb0.85)2Te3, PbTe and different barriers were fabricated by the common hot pressure method. Metals Fe, Mg and Ni were used as barriers between the two segments. The diffusion of different barriers between the barriers and bases were analyzed by electron microprobe analysis (EMA). The phase and crystal structures were determined by X-ray diffraction analysis (XRD). The thermoelectric properties were measured at 303 K along the direction parallel to the pressing direction. The results show that the compositional diffusion occurs when there is no barrier at the interface of the two segments, and the diffusion of Pb is most obvious; as the barrier material, the diffusion of metals Fe, Mg and Ni between different bases is not very obvious, and the thermoelectric properties of GTM is much better than that of the original segment.
In order to obtain thermoelectric materials with high figure of merit, the concept of Hollow (Vacuum) Quantum Structure or Effect and related thermoelectric materials design were proposed. To demonstrate the theory, the materials of (Bio.15Sb0.85)2Te3 with porous structure have been fabricated. Their thermoelectric properties and the microstructure were investigated and compared with their density structure. It was found that the porous structure could improve their properties greatly.
Guiying Xu, Tingjie Chen, Jianqiang Liu, and Zhangjian ZhouLaboratory of Special Ceramics and Powder Metallurgy, Materials Science and Engineering School, University of Science and Technology Beijing, Beijing 100083, China
