Rapid Synthesis And Thermoelectric Properties Analysis Of Re Doped Mg₂Si Based Thermoelectric Materials

Thermoelectric material is a kind of functional materials which can convert heat into electricity directly. The thermoelectric devices own some advantages as no pollution, no voice, maintainable and safety, which are of promising application value for thermoelectric generation and thermoelectric cooling, mainly used in the fields of low-grade heat power generation, aerospace and microelectronics. Magnesium Silicide is a kind of middle temperature thermoelectric materials, owing some advantages as the large effective carrier mass and mobility, abundance of its raw materials, low cost and environment friendly.In this paper, the method of Field-Activated and Pressure-Assisted Synthesis(FAPAS) combined with mechanical milling was used to realize the rapid reaction and densification of Mg₂Si based thermoelectric materials. Mg₂Si doped with rare earth (RE) Sc and Y were prepared, whose properties were compared with Sb and Sn doped Mg₂Si.According to the X-Ray Diffraction analysis, there were only sharp Mg₂Si peaks in all the XRD patterns, micro-content dopants did not change the main phase of Mg₂Si. The solid solubility of Sc, Y and Sb in Mg₂Si were about 2500ppm, 2000ppm and 5000ppm respectively. Both Sc, Y took the places of Mg in the crystal of Mg₂Si to form substitution solid solution, while Sb substituted Si. Y promoted the synthesis of Mg₂Si0.5Sn0.5.The fracture SEM image showed that Y didn't broke the regular strip like structure of Mg₂Si.The ZTmax of Mg₂Si prepared by FAPAS reached 1.42 times of that prepared by traditional hot pressed method. All the samples doped with different content of Sc, Y and Sb reached their best comprehensive electrical properties when intermingled quantity got to the solid solubility. Their maximum power factors were 2.76 times, 2.73 times and 2.03 times of that of nondoped Mg₂Si respectively. The thermal conductivity of sample doped with 2000ppm Y had been reduced by 20%, the figure of merit ZT achieved 2.30 times of pure Mg₂Si at 468K, and its ZTmax was 0.23, apparently higher than 0.18 which belongs to the latter. It is really a renewed approach to enhance the thermoelectric performances of Mg₂Si by doping rare earth elements and using FAPAS technology.