Fabrication and thermoelectric performance of textured n-type Bi_2(Te,Se)_3 by spark plasma sintering

摘要

The n-type Bi_2(Te,Se)_3 thermoelectric materials with preferred grain orientation have been fabricated through the spark plasma sintering (SPS) technique. The c-axis of the grains in the sintered samples were preferentially oriented parallel to the pressing direction, the orientation factor of the (0 0 l) planes changed from 0.4 to 0.85 with the sintering conditions. The anisotropy was investigated by measuring the electrical conductivities in the two directions perpendicular and parallel to the pressing direction. The optimal figure of merit ZT (ZT= alpha~2 sigma T/k) of the sintered materials in the direction perpendicular to the pressing direction was comparative to that of the zone-melted materials in the same crystallographic direction, while the bending strength reached about 80 MPa, which is 7-8 times of that of the zone-melted materials.