Investigation of microstructure and thermoelectric properties at different positions of large diameter pellets of Bi0.5Sb1.5Te3 compound

Abstract

The conversion efficiency of typical thermoelectric materials is still below 10% which leads the cost of the device was high. Recently, considerable attention has been paid to reduce the production cost and reliability of the performance. In this work, a low cost and an efficient method for large-scale production of high-quality thermoelectric powders via high-pressure gas atomization process and it have been sintered to a large diameter of pellets (50 mm) by spark plasma sintering process. The current and power densities of large diameter SPS processed specimens varied from center to edge portion. In order to verify the reliability of large diameter pellets, we investigated microstructure, thermoelectric and mechanical properties at different positions of pellets. The grain size variations could be clearly identified using SEM and EBSD techniques from center to edge part of pellets. Enhanced Seebeck coefficient and reduction of thermal conductivity for edge part of pellet were due to microstructure refinement which mainly occurs from temperature gradient during the sintering process. As a result, mechanical and thermoelectric properties were significantly enhanced. Ultimately, the thermoelectric performance of the large diameter pellets exhibits almost nearly equal from center to the edge which reaches 1.25 at 348 K.