Preparation of Bi0.5Sb1.5Te3 Thermoelectric Materials by Pulse-Current Sintering Under Cyclic Uniaxial Pressure

The effects of applying cyclic uniaxial pressure during the pulse-current sintering process on the crystal alignment and thermoelectric properties of p-type Bi_0.5Sb_1.5Te₃ were investigated. Sintering was performed at 673 K using pulse-current heating under 70 MPa or 100 MPa of cyclic uniaxial pressure. x-Ray diffraction patterns and electron backscattered diffraction analyses showed that application of the cyclic uniaxial pressure enhanced crystal grain orientation. The texture consisted of flattened crystal grains stacked in the thickness direction of the sintered materials. The hexagonal c-plane strongly tended to align in the direction perpendicular to the uniaxial pressure. Owing to the crystal alignment, the Hall mobility in the direction perpendicular to the uniaxial pressure became larger than that of equivalent samples prepared with a constant uniaxial pressure. As a result of the increase in Hall mobility, the resistivity of the material was decreased while the equivalent Seebeck coefficient was maintained and the power factor was improved.