Synthesis, structure and anisotropy of thermoelectric properties of Bi-=SUB=-2-=/SUB=-Te-=SUB=-2.7-=/SUB=-Se-=SUB=-0.3-=/SUB=- compound doped with samarium

Abstract

We study crystallographically textured thermoelectric materials with electronic conductivity based on bismuth telluride doped with samarium (Bi2-xSmxTe2.7Se0.3, where x=0, 0.05, 0.02, 0.05) obtained by the method of solvothermal synthesis and double pressing by the method of spark plasma sintering. The crystallographic texture was achieved by the spark plasma sintering of plate-like nanoparticles. The texturing axis [001] coincided with the direction of compression in the of spark plasma sintering process. An increase in the samarium concentration leads to a decrease in the radial size of the synthesized nanoplates, which facilitates the processes of rotation and sliding of particles relative to each other during pressing and, as a consequence, an increase in the anisotropy factor characterizing the degree of preferred grain orientation in the bulk material. Samarium doping affects the particle size of the initial powder, the average grain size in the bulk material and, as a consequence, the thermoelectric properties. It was found that the maximum of thermoelectric figure of merit weakly depends on the samarium content and falls in the range of ~(0.6-0.7), while the temperature position of the maxima noticeably shifts to higher temperatures with an increase in the Sm content. Keywords: thermoelectric materials, bismuth telluride, spark plasma sintering, texturing, anisotropy in properties.