Equal Channel Angular Extrued Bi_<0.5>Sb_<1.5>Te_3 Thermoelectric Compound
The effects of equal channel angular extrusion (ECAE) process parameters on microstructure and thermoelectric properties of the p-type Bi<SUB>0.5</SUB>Sb<SUB>1.5</SUB>Te<SUB>3</SUB> 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 (κ<SUB>ph</SUB>) which is independent of electrical properties. Maximum figure-of-merit (2.87×10<SUP>−3</SUP> K<SUP>−1</SUP>) 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.
- Materials transactions
Materials transactions 49(4), 889-891, 2008-04-01
The Japan Institute of Metals and Materials