Characterization of Bi-Te p-Type Thermoelectric Materials Produced by Uniaxial and Hydrostatic Sintering Technologies

The anisotropic structure of Bi₂Te₃-type thermoelectric materials makes them prone to mechanical vulnerabilities and inconsistent electrical and thermal properties according to microstructural orientation. In this study, sintered BiSbTe bodies were synthesized by spark plasma sintering (SPS), hot pressing (HP), and hot isostatic pressing (HIP) using p-type thermoelectric powders produced through oxide reduction. Changes in the microstructure and thermoelectric properties were investigated according to the sintering process. The thermoelectric properties of the samples produced by uniaxial methods (SPS and HP) were affected by the direction of pressing during sintering; the electrical and thermal conductivities differed by up to 30% depending on the orientation. In contrast, the hydrostatic HIP process did not impart such directionality; the difference in thermoelectric properties according to orientation was significantly reduced to less than 4%. Moreover, the sintered Bi₂Te₃ body produced by HIP showed outstanding thermoelectric performance at a much lower temperature than the samples produced by SPS or HP, with a maximum figure-of-merit (ZT) of 1.42 at 373 K.