Thermoelectric properties of anisotropy-controlled p-type Bi-Te-Sb system via bulk mechanical alloying and shear extrusion

Shear extrusion processing with combination of bulk mechanical alloying is proposed to yield the p-type Bi-Te-Sb materials from elemental granules. It has a well-developed texture so as to improve the electrical conductivity and thermoelectric properties. The shear extrusion processing in the Bi _0.4Sb_1.6Te₃ and Bi_0.5Sb _1.5Te₃ alloy green compact improves the preferred orientation factor of anisotropic crystallographic structure: F = 0.63 for Bi_0.4Sb_1.6Te₃ and F = 0.49 for Bi _0.5Sb_1.5Te₃, respectively. The electrical resistivity of Bi_0.4Sb_1.6Te₃ is well-controlled to be 0.989×10^-5Ωm, which is one-half of the hot-pressed specimen. Maximum power factor of Bi_0.4Sb_1.6Te ₃ is achieved to 4.33×10^-3W/mK². The bending strength of the material produced is also improved to be 120MPa, six times larger than that for the zone-melt specimen.