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Introduction of bismuth telluride crystals grow

wallpapers News 2021-11-19
Bismuth telluride and its alloys have anisotropic structural properties. The optimal value of thermoelectric properties of polycrystals with random grain orientation is relatively low. Single crystal or polycrystal with basically the same grain orientation has good thermoelectric performance. From the perspective of crystal integrity, the performance of a single crystal should be better than that of a polycrystal with a uniform orientation. Due to the existence of a cleavage plane with weak binding force in the crystal structure, compared with polycrystal, a single crystal is particularly prone to cleavage crack. So that increases the resistivity of single-crystal material and decreases the optimal value of thermoelectric properties. Therefore, bismuth telluride-based materials used in practice are polycrystalline ingots with uniform orientation. The main preparation processes of bismuth telluride polycrystals with uniform orientation in the laboratory include pre-treatment, crystal growth, and post-treatment.
Pre-treatment, is preparation for crystal growth.
First, weigh high purity raw materials following the alloy ratio and put them into quartz ampoules, and then reduce them. Melting in the atmosphere and full reaction, cooling solidification into ingots.
Crystal growth is to place the ingot in the crystal growth furnace and complete the crystal growth according to the set process parameters.
Bismuth telluride crystal growth methods include the Bridgman method, Zone Melt-ing method, and Czochralski method, and cloth method is commonly used. Richman method and zone melting method, domestic manufacturers adopt zone melting method.

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