In order to improve the thermoelectric properties, hot-pressing sintering andultra high pressure sintering methods were adopted to fabricate BiSb_x. The phase and crystalstructures were determined by X-ray diffraction analysis (XRD). The thermoelectric properties weremeasured at 303 K along the direction parallel to the pressing direction. The electric conductivityof the samples was measured at 303 K by the four-probe technique. To measure the Seebeckcoefficient, heat was applied to the samples placed between two Cu discs. The thermoelectricelectromotive force (E) was measured upon applying small temperature differences (DELTA T<2 deg C)between the both ends of the samples. The Seebeck coefficient of the samples was determined from thevalue of E/DELTA T. The results indicate that the thermoelectric properties of the samplesfabricated by UHPS (ultra high pressure sintering) method are much higher than that by HPS (hotpressing 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, theconcept of Hollow (Vacuum) Quantum Structure or Effect and related thermoelectric materials designwere proposed. To demonstrate the theory, the materials of (Bi_(0.15)Sb_(0.85))_2Te_3 with porousstructure have been fabricated. Their thermoelectric properties and the microstructure wereinvestigated and compared with their density structure. It was found that the porous structure couldimprove 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
