抄録
The n-type sintered Bi2Te2.85Se0.15, which is a composition of the practical thermoelectric material, were prepared by a hot pressing technique. The resistivity ρ, the Hall coefficient R, the thermoelectric power Q and the thermal conductivity κ were measured over the temperature range from 77 to 300 K. The range of the starting powder particle size was between 37 and 74 μm for the sintered specimen with the large values of the figure of merit Z=Q2⁄(ρκ). The values of Z were 1.60×10−3 and 2.24×10−3 K−1 for the specimens doped with HgBr2 and SbI3, respectively. During the heat treatment process in a hydrogen atmosphere, the amount of oxygen which acted as a donor in the sintered Bi2Te2.85Se0.15 was reduced and then the electron concentration was decreased. However, the increase in electron mobility resulted in improvement in Z. In the case of the sintered specimens doped with HgBr2, a large value of Z was obtained for the specimens prepared form the deoxidized powder compared with those deoxidized after sintering. The value of Z was 2.56×10−3 K−1 which was equal to the utilized unidirectional solidified material. At 240 K, a remarkably large value of Z=3.70×10−3 K−1 was obtained for the specimen doped with SbI3 due to the high electron mobility and the low lattice thermal conductivity.
