| The best materials for thermoelectric refrigeration modules at ambient temperature are Bi2Te3 based alloys. These alloys are conventionally produced in single crystal form by directional solidification such as the Bridgman and the Czochralsky techniques. Powder metallurgy associated with a hot working process involving plastic deformation, such as extrusion, seems an interesting alternative for the processing of these alloys. Indeed, these processing routes could lead to cost reductions and gain of productivity. Moreover, the polycrystalline form of Bi2Te3 alloys offers better mechanical properties, lowering the rejects costs during the manufacturing of refrigeration modules. However, they also have lower thermoelectric efficiency than single crystal.; The extrusion process is of particular importance because it enables the production of dense materials with a crystallographic texture that is essential for obtaining good thermoelectric performance. The extrusion process however induced heterogeneity of the plastic deformation which affects directly the alloys properties. Experimental results and numerical simulations obtained using a finite element software FORGE2RTM, were used to study of the influence of certain parameters of the extrusion process on the properties of the alloys.; Defect free rods can be produced by hot extrusion process, for both n- and p-type alloys, with good properties. The extruded alloys show an increase of 40% of the mechanical properties compared to single crystals. Also, the p-type alloys have a figure of merit of 3,2 x 10-3K -1, which is comparable of the value obtain for alloys produced by melt growth. The n-type has a figure of merit of 2,8 x 10 -3K-1, that is about 15% lower than single crystals but higher than the values obtained by the majority of other groups working on polycrystalline alloys. |
