Traditionally, since the 50-ies of the previous century, the production of thermoelectric materials (TEM) was carried out mainly by crystallization from a melt. However, the hot extrusion is hugely promising and technological method. It provides a production of the rods of thermoelectric materials with desired geometrical configuration and satisfied high mechanical and thermoelectric properties [1]. These mechanical properties play the particular importance at TEM applications in thermal generators and cooling micromodules.

      The technological process of extrusion involves a lot of consecutive operations: synthesis of solid solution for required composition, grinding and dispersion of micron-sized powder, production of briquettes by powder cold pressing, hot extrusion and annealing of extruded rods. One of the factors, which may essentially impair the thermoelectric properties, is an interaction of the material with oxygen (oxidation process). Therefore all operations with its powder are carried out in an inert atmosphere.

      The following questions are discussed in this presentation:
1. The production of extruded material from a micro- and nanopowder mixture.
2. The application of initial rod materials produced by different methods (preliminary extrusion and zone melting).
3. The influence of extrusion ratio on TEM properties of extruded rods.

      The structure and texture distributions along a rod length were investigated by metallographic and X-ray methods for a compound Bi_xSb_2-xTe₃ extruded from solid solution. Some basic regularities of stucture formation for this material have been published in [2]. The mechanical properties have been investigated by means of the permanent record of the deformation diagram (load-deformation) in temperature range 293-623 K for the samples, which were cut in extrusion direction and perpendicular to it. The thermoelectric properties of extruded samples were measured by Harman’s method.

      The measurements at room temperature of mechanical and thermoelectric properties in p-type TEM samples showed the strength  ~ 150 MPa and the thermoelectric efficiency ~ 3.5*10^-3 K^-1, which satisfy the modern international standards.

 ACKNOWLEDGMENTS

This investigation was supported by JSC “ROSATOM” (the state contract Н.4б.44.90.13.1050) and Russian Foundation for Basic Research (the grants: 12-02-90027-Bel, 12-02-01126).

References

[1] Sabo Ye.P. // Journal of Thermoelectricity. 2005. V.3. P. 52-68.

[2] Lavrentev M.G., Osvenskii V.B., Mezhennii M.V. et al // Journal of Thermoelectricity.2012.V. 4.P. 36-42.

1. POSTER: The production of bulk thermoelectric materials based on bismuth and antimony chalcogenide solid solutions by hot extrusion, Microsoft Office Document, 0MB

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