Thermoelectric Properties of Cu-doped Bi₂Te_2.85Se_0.15 Prepared by Pulse-Current Sintering Under Cyclic Uniaxial Pressure

Abstract

N-type Cu-doped Bi₂Te_2.85Se_0.15 thermoelectric materials were prepared by pulse-current sintering under cyclic uniaxial pressure, and the effect of the cyclic uniaxial pressure on texture and thermoelectric properties was investigated. Cu _x Bi₂Te_2.85Se_0.15 (x = 0−0.03) powder prepared by mechanical alloying was sintered at 673 K using pulse-current heating under 100 MPa of cyclic uniaxial pressure. X-ray diffraction patterns and electron backscattered diffraction analyses showed that the cyclic uniaxial pressure was effective for texture control. The flattened crystal grains were stacked in the thickness direction of the sintered materials and the hexagonal c-plane strongly tended to align in the direction perpendicular to the uniaxial pressure. As a result of this crystal alignment, the electrical resistivity in the direction perpendicular to the uniaxial pressure became smaller than that of equivalent samples prepared with a constant uniaxial pressure. The smaller resistivity led to a larger power factor, and the figure␣of merit was improved by the application of cyclic uniaxial pressure.