Abstract
In this study, Ingots of (Bi, Sb)2Te3 thermoelectric material with p-type conductivity have been obtained by hot extrusion. The main regularities of hot extrusion of 30 mm rods have been analyzed with the aid of a mathematical simulation on the basis of the joint use of elastic-plastic body approximations. The phase composition, texture and microstructure of the (Bi, Sb)2Te3 solid solutions have been studied using X-ray diffraction and scanning electron microscopy. The thermoelectric properties have been studied using the Harman method. We show that extrusion through a 30 mm diameter die produces a homogeneous strain. The extruded specimens exhibit a fine-grained structure and a clear axial texture in which the cleavage planes are parallel to the extrusion axis. The quantity of defects in the grains of the (Bi, Sb)2Te3 thermoelectric material decreases with an increase in the extrusion rate. An increase in the extrusion temperature leads to a decrease in the Seebeck coefficient and an increase in the electrical conductivity. The specimens extruded at 450 °C and a 0.5 mm/min extrusion rate have the highest thermoelectric figure of merit (Z = 3.2 × 10−3 K−1).
Highlights
Bismuth and antimony chalcogenide based solid solutions are the main thermoelectric materials used by the manufacturers of thermoelectric cooling and generator modules [1,2].The materials of thermoelectric module cells work under severe thermal conditions and loads
The specimens extruded at 450 ◦ C with a 0.5 mm/min extrusion rate have the highest thermoelectric figure of merit (Z = 3.2 × 10−3 K−1 )
30 mm diameter ingots of the (Bi, Sb)2 Te3 thermoelectric material were produced by hot extrusion
Summary
Bismuth and antimony chalcogenide based solid solutions are the main thermoelectric materials used by the manufacturers of thermoelectric cooling and generator modules [1,2].The materials of thermoelectric module cells work under severe thermal conditions and loads. The temperature gradients produced in these materials during operation may induce large thermal stresses which can cause destruction of the material and module cell failure. For this reason, the technology of these materials is the key aspect in the fabrication of thermoelectric devices, its importance being greater when it comes to the fabrication of miniaturized cooling systems for microelectronics, optoelectronics, and laser devices where the thermoelectric material quality and reliability requirements are extremely stringent [3]. Bismuth and antimony chalcogenides have a rhombohedral structure with the R3m symmetry group, and their physical properties are anisotropic [4]. Their parameters, such as their electrical conductivity and heat conductivity in the direction of the third order
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