Interconnected effects of Sm-doping on grain structure and transport properties of the textured Bi2-xSmxTe2.7Se0.3 compounds

Abstract

Textured Bi2-xSmxTe2.7Se0.3 compounds with x ​= ​0; 0.005; 0.01; 0.02; 0.05; 0.1; 0.2 and 0.3 were prepared by using solvothermal synthesis and spark plasma sintering of starting powders. Sm-doping results in several interconnected effects. First of them is reducing in size of particles in starting powders with increasing x. This effect is attributed to increasing in ionic bonding fraction in polar covalent Bi(Sm)-Te bonds, which occurs at increasing Sm content due to difference in electronegativity of Bi and Sm. With increasing x, grain size in bulk samples is also reducing, which is governed by relevant changing in the size of particles. This effect also results in enhancing in texturing degree in samples at gradual increasing x. Finally, grain size effects on the specific electrical resistivity and the thermal conductivity are observed in bulk samples with different grain size. With increasing the grain size, the resistivity increases, whereas the total thermal conductivity decreases. These features are due to electron scattering by grain boundaries.