Thermoelectric Performance of Bi_0.5Sb_1.5Te₃/Sb Composites Fabricated by Electroless Plating and Spark Plasma Sintering

This study reports semi-metal/semi-conductor composites with enhanced thermoelectric performance that results from interface effects between Sb clusters and the Bi_0.5Sb_1.5Te₃ matrix. The Sb clusters were dispersed on the surface of Bi_0.5Sb_1.5Te₃ powders by electroless plating and then the powders were rapidly compacted by spark plasma sintering at 673 K and 50 MPa. The thermoelectric properties for Bi_0.5Sb_1.5Te₃ and Bi_0.5Sb_1.5Te₃/Sb bulk samples were measured in the temperature range of 300 K to 500 K. The electrical conductivity of Bi_0.5Sb_1.5Te₃/Sb composites was enhanced at room temperature due to the increase in carrier concentration with increasing Sb content. The enhancement in the power factor of Bi_0.5Sb_1.5Te₃/Sb composites was due to a high Seebeck coefficient at high measured temperature. Moreover, the Sb clusters acted as effective phonon scattering centers, which decreased the lattice thermal conductivity at high temperature. In comparison with Bi_0.5Sb_1.5Te₃, the maximum value of ZT for Bi_0.5Sb_1.5Te₃/Sb (2.8 wt.%) samples was enhanced from 0.21 to 0.54 at 500 K. Consequently, the optimal operation temperature of Bi_0.5Sb_1.5Te₃/Sb composites shifted to higher temperature compared to that for Bi_0.5Sb_1.5Te₃ bulk.