SYNTHESIS, MICROSTRUCTURE AND THERMOELECTRIC PROPERTIES OF COMPOSITE MATERIAL Bi2Te2.7Se0.3Teδ OBTAINED FROM ASYMMETRIC

Composite materials Bi2Te2.7Se0.3 /Teδ with varying concentration (δ = 0.15; 0.2; 0.25 and 0.3) were obtained by solvothermal synthesis of the initial powders and their subsequent spark plasma sintering. During the sintering process, the samples are textured, as a result of which the lamellar grains are arranged in layers perpendicular to the direction of pressure application during sintering (the direction of the texture axis). At magnification, the concentration of over-stoichiometry tellurium decreases the degree of texturing. The concentration of tellurium does not affect the average grain size. Super-stoichiometric tellurium is distributed along the grain boundaries, as a result of which a structure characteristic of composite materials is formed. The release of tellurium at the grain boundaries leads to a change in the thermoelectric properties of the obtained materials. The electrical resistivity naturally increases, and the total thermal conductivity decreases with an increase in the concentration of overstoichiometry tellurium.