Preparation method and extrusion die of bismuth telluride-based thermoelectric material

Abstract

The invention discloses a preparation method of a bismuth telluride-based thermoelectric material and an extrusion die. A mold groove of the extrusion mold comprises an inlet section, a connecting section and an outlet section, and the inlet section and the outlet section are located at the two ends of the connecting section correspondingly. The connecting section comprises an equal-diameter bent pipe section and a variable-diameter section; the equal-diameter bent pipe section is connected with the inlet section and the variable-diameter section; the variable-diameter section is connected with the outlet section and the equal-diameter bent pipe section; the diameter of the outlet section is smaller than that of the inlet section. The preparation method comprises the following steps: putting a bismuth telluride-based thermoelectric material crystal bar ingot into an extrusion die, and carrying out hot extrusion. According to the preparation method, the bismuth telluride-based thermoelectric material is prepared from the crystal bar cast ingot through the hot extrusion method by using the extrusion die with the bent shape and the inlet diameter larger than the outlet diameter, the plastic deformation degree and deformation uniformity of all parts of the thermoelectric material are enhanced, and dual improvement of thermoelectric performance and mechanical performance is achieved.

Description

technical field [0001] The invention relates to the technical field of thermoelectric materials, in particular to a preparation method and an extrusion die of a bismuth telluride-based thermoelectric material. Background technique [0002] Thermoelectric materials are functional materials that directly convert thermal energy and electrical energy by utilizing the Seebeck effect and Peltier effect of semiconductors. Thermoelectric refrigeration devices based on the Peltier effect have the characteristics of small size, no moving parts, no noise, and high precision. They have been widely used in local refrigeration and temperature control of electronic components in many fields such as microelectronics, computers, and aerospace. In recent years, with the rapid development of the 5G industry, micro thermoelectric cooling devices have become one of the key components for thermal management of high-speed communication optical modules. [0003] At present, bismuth telluride-based...

AI Technical Summary

Problems solved by technology

At present, there are three mainstream processes for the batch synthesis of bismuth telluride materials. The first process is to grow rod-shaped crystals by the zone melting method. This method can achieve good grain orientation and ensure thermoelectric properties along the growth direction. Currently, the zone melting method grows The maximum ZT value of the N-type material can reach 0.9, and the maximum ZT value of the P-type material can reach 1.1; however, the material obtained by this process has coarse grains, poor mechanical strength, and is prone to dissociation. Composition segregation leads to poor uniformity of mass-produced materials; the second process is the powder metallurgy method, that is, the raw material powder is mixed and alloyed by ball milling, or the ultra-fine powder of bismuth telluride is obtained by melting and spinning. Densification through sintering; this process has a high degree of powder mixing uniformity, and uses the fine-grain strengthening effect to improve the mechanical strength of the material, but the degree of orientation is greatly reduced due to grain refinement, and it is easy to introduce external impurities or Oxidation is caused, and the performance is lower than that of the preferred orientation ingot; the third process is the hot extrusion method, which performs thermoplastic densification of the zone-melted ingot under pressure, and promotes grain turning while refining the grain. The degree of texture orientation can not only increase the mechanical strength of the material, but also maintain the good thermoelectric properties of the zone melting crystal; in addition, because the hot extrusion method is continuous and suitable for commercial mass production, it has potential development value

[0004] Chinese patents CN101985776A and CN112893497A and U.S. Patent US6596226B1 disclose several coaxial hot extrusion die devices. The mold is placed in a hot extrusion furnace heated by the overall cavity, and the crystal rod with a thicker upper diameter is heated at a certain temperature and pressure. The lower section is extruded into the lower section through thermal deformation to become a thin rod; in this coaxial hot extrusion process, since the degree of extrusion on the edge of the edge crystal rod and the friction of the inner wall are greater than that of the central area of ​​the crystal rod, the The degree of plastic deformation in the diameter direction is severely uneven, and the surface of the extruded ingot is very prone to cracks; at the same time, the overall external heating method makes it difficult to independently and precisely control the local temperature fields of the upper section, variable diameter section, and lower section of the hot extrusion die, eventually causing The strength and thermoelectric properties of extruded boules are difficult to be uniform and stable

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