Powder metallurgy method making thermoelectric materials bismuth telluride (Bi2Te3) alloy, working temperature isclose to 450 ℃ can be used in the manufacture of household refrigerator, air conditioner, small detectors and sensors, etc. Bismuth telluride with a small amount of antimony telluride (Sb2Te3) alloying can form P type semiconductor solid solution, and with a small amount of bismuth selenide (Bi2Se3) alloying can form N type semiconductor solid solution. Bismuth telluride, it and other components to forming alloy have highly anisotropic structure. the most commonly used method making bismuth telluride alloy is single crystal directional crystallization. But this method is low productivity, segregation, and poor mechanical properties.
Canada after three years development, has developed a method of of producing bismuth telluride alloy by powder
metallurgy. It is mechanical alloying 2-5 mm diameter granular pure elements (such as Bi, TeSeSb) powder in a ball mill, after about 3h can be obtained for 5~10 m particle size alloy powders. Powder is cold pressed under the pressure of 360 mpa , compact body relative density of 80%, And hot extrusion in inert atmosphere into the 963.5 mm bar, extrusion temperature 420-490 ℃. The extrusion speed of 2 mm/min, products is dense after hot extrusion. Although extrusion materials is polycrystalline, but have no difference thermoelectric performance with single crystal material.
Material compression strength is 105 mpa, and the single crystal materials is only 20 mpa, grain boundaries hinder crack propagation of polycrystalline materials. This is helpful to improve its mechanical properties and the reliability of the thermoelectric devices. Manufacturing thermoelectric materials of powder metallurgy method can reduce the production cost, increase productivity, and has no damage.
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