Thermoelectric Material β-FeSi₂ Prepared By Self-propagating High Temperature Reaction Synthesis And Heat Treatment And The Study Of Thermoelectric Performance

Since the 1990 s, with the continuous development of world economy and science technology, the overuse of primary energy have caused the greenhouse effect, haze, acid rain and other environmental issues. Eventually, the energy and global environmental crisis will become more and more serious. Therefore, the target of national material researcher is the research and development of no pollution, no noise and high efficiency energy conversion material that can substitite for primary energy. In addition, if we can combine the thermoelectric conversion technology with solar power and nuclear fusion, and reasonably use the continuing and pollution- free energy, so as to the sustainable development of energy will be realized, also the environmental crisis will be slowed down. Among them, the β-FeSi2 has good high temperature oxidation resistance and high temperature performance of the thermoelectric conversion. Furthermore, the β-FeSi2 is rich in natural resources and non-toxic, the price is low. So the β-FeSi2 is a kind of great application value of high temperature thermoelectric conversion material.The research object of this paper is the thermoelectric materials β-FeSi2 that can achieve thermal energy and electrical energy interconversion.we use the Fe powder, Si powder and KNO3 as the raw material.The method of preparation thermoelectric material β-FeSi2 is Self-propagating High-temperature Synthesis(SHS) process which is simple, energy-saving and instantaneous. Using XRD and SEM analysed and discussed the influence of different process parameters on the synthetic product organization structure. These parameters mainly include raw material granularity, compacting pressure, heat treatment temperature and heat treatment time. In addition, through the doped with the different element of Co, Using XRD, SEM analysed the self-propagating high temperature synthesis product and heat treatment sample of phase composition and the morphology of the organization. Furthermore, using vacuum sintering machine pressed the loose powder sample for hot pressing molding, and made its densification. Then we tested, analyzed and discussed the the thermoelectric parameters seebeck coefficient, resistivity and thermal conductivity of the block sample preparation. So as to we can lay the foundation for the preparation of thermoelectric materials β-FeSi2 which performance is good.The research showed that: 1.Both the increasing of the compacting pressure or the decreasing of the raw material granularity can make the sample density increase and the reactions are more likely to happen. When the pressure is 120 Mpa and the raw material granularity is 75 ~ 90 micronmeters, the reaction rate is the fastest, the product is no caking phenomenon between particles; 2.When the heat treatment temperature is 840 ℃, the holding time is 3 hour, the diffraction peak intensity of β phase enhanced obviously, the conversion rate of β-FeSi2 is the highest and the mixed phase α phase disappeared basically. So the best heat treatment process is that the heat treatment temperature is 840 ℃ and the holding time is 3 hour. 3. Doping Co had no effect on the phase composition of self-propagating high temperature synthesis product. When doping 0.05% Co, the diffraction peak intensity of α phase is the strongest, and the diffraction peak intensity of ε phase is the weakes. The α phase in the eutectic organization has good crystallinity and higher content.After heat treatment, the β-FeSi2 has good crystallinity and high purity. 4. Through the study of β-FeSi2 thermal parameters, we found that compared the thermal parameters of the sample with not mixed, after mixing elements Co, all the thermal parameters have obvious changes. The Seebeck coefficient increased, the resistivity and thermal conductivity reduced.