Thermoelectric performance of textured Bi2Te 3-based sintered materials prepared by spark plasma sintering

ABSTRACTThermoelectric performance of polycrystalline materials is greatly influenced by their microstructures including grain sizes, grain boundaries, grain orientations in anisotropic compounds, etc. The material microstructures are sensitive to the preparation processes and the starting materials. In the present study, n-type and p-type Bi2Te3-based sintered materials with highly preferred grain orientations have been fabricated through a spark plasma sintering (SPS) technique, by controlling the particle sizes of the starting powder and other sintering process parameters. The obtained textured Bi2Te3-based materials show a high mechanical strength as 80MPa in bending strength, which is 7 to 8 times as that of the melted ingot materials, and a significant anisotropy in thermoelectric transport properties. The optimal figure of merit (ZT) of the sintered materials in the direction perpendicular to the pressing direction (with c-axis preferred orientation) is comparable to that of the zone-melted ingots in the same crystallographic orientation.