Thermoelectric Properties of N-typer Bi₂Te₃-PbTe Graded Thermoelectric Materials with Different Barriers

In order to investigate the adaptability of thermoelectric materials system with different barriers to functional graded thermoelectric materials, n-type Bi₂Te₃ and PbTe two segments graded thermoelectric materials (GTM) with different barriers were fabricated by conventional hot pressing method. Metals Cu, Al, Fe, Co and Ni were used as barriers between two segments. The effects of different barriers on thermoelectric properties of GTM were investigated. The phase and crystal structures were determined by x-ray diffraction analysis (XRD). The distributions of different compositions were analyzed by electron microprobe analysis (EMA). The thermoelectric properties were measured at 303 K along the direction parallel to the pressing direction. The electric conductivity of samples was measured at 303 K by the four-probe technique. To measure the Seebeck coefficient, heat was applied to the samples, which were placed between two Cu discs. The thermoelectric electromotive force (E) was measured upon applying small temperature differences (△T<275 K) between the both ends of the samples. The Seebeck coefficient of the samples was determined from the E/△T.