Space Growth of Bismuth Telluride Based Thermoelectric Semiconductive Crystals

Bismuth telluride based thermoelectric semiconductors are high performance thermoelectric materials in the low temperature range (about 300℃), which have important applications in thermoelectric cooling and precise temperature control of electronic devices, and have broad application prospects in thermoelectric generation through industrial waste heat recovery. Bismuth tellurides are mainly produced with zone melting method, and their ZT value is around 0.8. The ZT value needs to be further improved as bismuth telluride is applied to commercial domain. Although alloying and doping are effective methods to improve the ZT value, they will make the chemical composition of bismuth tellurides become more complicated. The inherent problems of zone melting method, buoyancy force convection and wall effect, are revealed under gravity, and will make the fluctuation of chemical composition and thermoelectric properties become larger. Microgravity in space may eliminate the buoyancy force convection and wall effect, and can improve the chemical homogeneity and thermoelectric properties of bismuth tellurides. In this paper the development of zone melting of bismuth tellurides under microgravity is reviewed, and the following researched on the zone melting of bismuth telluride that will be carried on the Shijian-10 satellite and the Tiangong-2 space station is prospected.