Influence of powder morphology on thermoelectric anisotropy of spark-plasma-sintered Bi–Te-based thermoelectric materials

The influence of the starting powders’ morphology on the thermoelectric anisotropy of Bi–Te-based thermoelectric materials that are fabricated by spark plasma sintering has been investigated. Starting powders with three types of morphologies are prepared through a chemical reaction method (nano-sized particles with a spherical shape), a conventional pulverization method (flake-like shape) and a gas atomizing method (spherical shape). The thermoelectric anisotropy of each sintered body is determined by measuring the electrical resistivity and thermal conductivity in both the parallel and perpendicular directions to the spark plasma sintering pressing direction. The p-type Bi0.5Sb1.5Te3.0-sintered body that is composed of the spherically shaped powder has isotropic thermoelectric properties, while the same material composed of the flake-like powder shows anisotropic behavior. The n-type Bi2Te3 sintered body has a relatively small anisotropy when it is composed from the spherically shaped powder.