| Thermoelectric materials is through the solid internal carrier and phonon transmission and their interactions, with each other directly in order to realize the energy and electrical energy conversion function of a new type of semiconductor material. Thermoelectric materials can make use of waste heat to generate electricity, to realize the multiple utilization of energy and improve energy efficiency; At the same time can also use the adverse effect to realize the cooling or heating, is a very promising energy material. Mg2Si is a400-800k temperature range stable performance excellent potential thermoelectric materials, having a low density, high temperature resistant, high specific strength and other excellent performance. It is generally believed that by reducing the grain size to the nano and appropriate dopingis the necessary way to obtain high-performance Mg2Si thermoelectric materials.This paper uses MgH2instead of pure Mg, lies in the in situ reaction and sintering process, the decomposition of MgH2into Mg and Si direct reaction of Mg2Si, the grain boundary between the more pure; in addition, the by-products of the reaction of H2, has better reducibility, further reducing the generated due to the oxidation of MgO. At the same time by solid state reaction at low temperature and electric field activated pressure assisted synthesis (Field-Activated and Pressure-Assisted Synthesis, referred to as FAPAS) technology, using the one step synthesis process for the preparation of high purity nano Mg2Si semiconductor materials, and further improvement of its reaction process, preparation of Mg2Si based thermoelectric materials Bi element doping. Comparative analysis of the advantages and disadvantages of one step synthesis of Mg2Si and the influence of doping in Mg2Si based thermoelectric material of Bi doping on the thermoelectric properties.The results show that, by one step synthesis of bulk Mg2Si based thermoelectric materials has the advantages of fast speed, high efficiency, and pure product and has the characteristics of nano structure, which effectively reduces the thermal conductivity, the thermoelectric properties of the materials to improve the overall. At the same time, a modest excess of Si is helpful to improve the thermoelectric properties of materials, mixing ratio of1.95:1samples in the thermoelectric properties are superior to the ratio of2:1samples, at725℃, the former ZT to up to0.54. |
