Self-propagating High-temperature Synthesis-hot Pressing Fabricate Thermoelectric Material β-FeSi₂

Thermoelectric materials, which can realize thermoelectric conversion directly withoutany mechanical equipments and noise, are attractive as a kind of save-energymaterials. Withincreasing energy crisis，green energy is explored．So doing research and development ofβ-FeSi₂as a potential thermoelectric material possesses important practical significance．It hashigh Seebeck coefficient, abundance as a raw material, low cost, high oxidation resistance,non-toxicity, and high working temperature. Because β-FeSi₂with the above advantages, ithas broad application prospects, and one that fits well with the operating temperatures ofindustrial furnaces, automobile exhausts, and incinerators. However, the synthesis of β-FeSi₂is very difficulty.In this paper, we synthesis β-FeSi₂by the way of SHS-hot pressing technology. Thispaper study the following aspects:1.In the process of Intermediate products α-Fe₂Si₅intoβ-FeSi₂, when the temperature is fixed at4min, we looked for the best hot insulation pressingtemperature and pressure through selecting different holding time and pressure, and thenconcluded the most reasonable of hot press process parametersï¼›2.In order to make thecombustion synthesis products contain only α-Fe₂Si₅, we studied the composition of thecombustion synthesis to find the most reasonable proportion of Fe and Si in the batching stageby changing the Si contentï¼›3.The best doping ratio were explored through comparativeanalysis of different Cu doping content of synthetic productsï¼›4.By doped with differentcontent of Al, we analysis of the phase composition and morphology of the synthetic productsof the different Al content.The experimental results include the following main points:1.The main products ofcombustion synthesis are α-Fe₂Si₅and Si when the atomic ratio of Fe to Si is1:3and0.5at%copper is doped. When the temperature is800℃, the parts of β-FeSi₂re-transformed intoα-Fe₂Si₅, pressure increased contributes to the products density increase and α-Fe₂Si₅transformed into β-FeSi₂ï¼›2.When the atomic ratio of Iron, silicon is1:2.5, the combustionsynthesis sphere products only contain α-Fe₂Si₅and eliminating ε-FeSi phase. The followingtest and analysis results have larger deviation whether combustion synthesis sphere productsare clean using ultrasonic cleaning device.when the cleaning is insufficient, the ε-FeSi in theslag buildup in the sphere, and then they will make the synthesis process of β-FeSi₂is notentirelyï¼›3.In the process of Eutectoid reaction αâ†'β+Si to generate β-FeSi₂, a small amount ofCu doping can significantly improve the speed of response, and the reaction speed willincrease with increasing Cu content.The particles of reaction are uniform size be seen by the fracture SEM micrographs,and the Si particles dispersed in itï¼›4.Al does not affect the phasecomposition of the combustion synthesis shere products, the sphere products of combustionsynthesis are still α-Fe₂Si₅, but Al doping can improve the utilization of the original powder，and the effect of doped Al is not obviously in the process of αâ†'β+Si. In order to avoidexcessive Al, α-Fe₂Si₅completely transformed into β-FeSi₂while2at%Al is doped inoriginal powder adds0.2at%Cu to it. The hot pressed samples achieve the highest peak ofthe β phase.