2008 Volume 49 Issue 4 Pages 889-891
The effects of equal channel angular extrusion (ECAE) process parameters on microstructure and thermoelectric properties of the p-type Bi0.5Sb1.5Te3 compound have been investigated. ECAE was carried out under various temperatures (653 K, 693 K, 733 K) and ram speeds (0.5 mm/s, 1 mm/s, 2 mm/s). Fraction of recrystallized grains and grain size was found to be increase with lower ram speed and higher deformation temperature. As a result, Seebeck coefficient increased, and electrical resistivity and thermal conductivity decreased. The decrease in thermal conductivity was attributed to the decrease of lattice thermal conductivity (κph) which is independent of electrical properties. Maximum figure-of-merit (2.87×10−3 K−1) was achieved in as-ECAE’ed specimen at 733 K and at ram speed of 0.5 mm/s. This value was found to be 6% higher than that of as-sintered specimen.