Bismuth telluride is a gray powder with the molecular formula Bi2Te3. Bismuth telluride is a semiconductor material, which has good electrical conductivity, but poor thermal conductivity. Although the risk of bismuth telluride is low, it can be fatal if ingested in large amounts. However, this material can allow electrons to move on its surface without energy consumption at room temperature, which will bring a leap in the operating speed of the chip, meanwhile it can greatly improve the operating speed and work efficiency of computer chips.
Bismuth telluride powder materials can be processed into various commonly used devices. The more commonly used preparation methods are: zone melting method, Bridgeman method, single crystal pulling method, plasma activated sintering method and hot pressing Sintering method, the preparation of single crystal materials often use zone melting method, Bridgman method and single crystal pulling method.
1. Zone melting method: It is a method of growing single crystals by melting and crystallization of polycrystalline ingots. The rod-shaped polycrystalline ingot is melted in a narrow area, and the rest is kept solid, and then a molten area is moved along the length of the ingot, so that the rest of the entire ingot is melted and crystallized again.
2. Bridgman method: It is a commonly used crystal growth method, also known as the crucible descending method. This method is to put the material for crystal growth in a cylindrical crucible, and slowly pass through a high-frequency furnace or resistance furnace with a temperature gradient. The temperature of the furnace should be slightly higher than the melting point of the crystal material. When the crucible containing the crystal material drops to the heating center of the furnace, the material begins to melt; when the crucible continues to fall slowly, after passing the heating center of the furnace, the temperature at the bottom of the crucible begins to drop first, when the temperature drops When the melting point of the crystalline material is below, the crystalline material begins to crystallize until the crucible is completely cooled, and the crystal continues to crystallize and grow. This method is mainly suitable for common ionic compounds, such as halides of alkali metals and alkaline earth metals.
3. Czochralski method: It is the method that Chukraski invented in 1917 to grow high-quality single crystals from the melt, so it is also called Chukraski method. This method is to put crystal material in the crucible. Then heat the crucible, after the crystal material is completely melted, use the pull rod to pull the crystal material out of the melt, and under proper temperature control, the seed crystals pulled out during the cooling period are continuously rearranged, then growing crystals.
