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 Bi0.4Sb1.6Te3 and Bi0.5Sb1.5Te3 alloy green compact improves the preferred orientation factor of anisotropic crystallographic structure: F = 0.63 for Bi0.4Sb1.6Te3 and F = 0.49 for Bi0.5Sb1.5Te3, respectively. The electrical resistivity of Bi0.4Sb1.6Te3 is well-controlled to be 0.989 x 10(-5) Omega m, which is one-half of the hot-pressed specimen. Maximum power factor of Bi0.4Sb1.6Te3 is achieved to 4.33 x 10(-3) W/mK(2). The bending strength of the material produced is also improved to be 120 MPa, six times larger than that for the zone-melt specimen. (C) 2003 Elsevier B.V. All rights reserved.