| As global environmental pollution and the growing energy crisis,the development of new environmentally friendly energy alternative materials have attracted more and more concern all over the world.β-FeSi2 is a semiconductor thermoelectric materials that can work in high temperature environments,has high temperature thermoelectric conversion function in the temperatures range of 500900℃.β-FeSi2 have many advantages such as oxidation resistance, rich sources of raw materials, stable performance and prices, more over, there are not significantly affect on the preparaed thermoelectric performance when choose low purity of industrial raw material.In addition,doped with trace elements of Cu,Co,B,Al etc during the preparation ofβ-FeSi2 formed p-type semiconductor or n-type semiconductor can improve the thermoelectric performance ofβ-FeSi2 obviously and avoid the difficulty of making thermoelectricity components due to the different thermal expansion coefficient of the semiconductor two feet materials.Because of the above advantages,β-FeSi2 has become a promising thermoelectric materials.In this paper,we synthesis the thermoelectric materialsβ-FeSi2 by the way of combustion synthesis-heat treatment process, with simple way to prepare high purity ofβ-FeSi2. This technology can improve the practical application value ofβ-FeSi2 and reduce the cost of application of this materials widely and investment in industrial production directly. We take the powders of Fe,Si and KNO3 as raw material,increase the mechanical energy through the ball mill mixing that be helpful for reactants the synthesis reaction. This paper study the following aspects:1.Comparative analysis the effects of doped copper and no-doped copper on final synthesis productsβ-FeSi2, summarized the doped mechanism of formation p-type or n-type semiconductor. 2.Effect of different silicon content on the productivity of synthesis materialβ-FeSi2 by change the atomic ratio of Fe to Si in the mixing stage. 3.For combustion synthesis intermediate productsα-Fe2Si5, we selected different insulation temperature and holding time to annealing treatment by box resistance furnace, then analyzed by means of X-ray diffraction(XRD), and summarized reasonable treatment parameters of phase transformation ofα-Fe2Si5→β-FeSi2.The results show that 0.5 at% copper doped in heat-treatment process could accelerate eutectoid reaction precess (α→β+Si),the transformation fromα-Fe2Si5 phase toβ-FeSi2 phase is completely and finally formed P-type semiconductor. In xrd spectrum of combustion products not doped Cu after heat-treatment,α-Fe2Si5 phase always be found.Thermoelectric materialβ-FeSi2 was prepared by the method of combustion synthesis-heat treatment process, Samples ofβ-FeSi2 were prepared in the mixing stage and the atomic ratio of Fe to Si was 1:3,the XRD analysis shows that the excessive content of silicon accelerated the phase transformation of Si+ε→β,andεphase was eliminated in a large extent,the content ofβ-FeSi2 increased.When the heat treatment temperature was 800℃,α-Fe2Si5 phase eliminated absolutely in 2h,when the diffraction peak ofβ-FeSi2 displayed the maximum value.Further more,the particle size of products reduced significantly,large-size particles disappeared,and the internal structure of products became more uniform.
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