硅酸盐学报

硅化镁(Mg2Si)是一种窄带隙n-型半导体,具有高的电导率和低的热导率且无毒无污染、耐腐蚀,是很有潜力的环境友好型中温域热电材料。实验用高纯镁(Mg)粉和硅(Si)粉,系统研究了放电等离子烧结制备Mg2Si热电材料的工艺过程。测试了样品的密度。用X射线衍射、场发射扫描电镜表征了样品的相组成和显微结构。结果表明:Mg,Si完全固相反应的温度为823K,适度过量的Mg含量对纯相Mg2Si的获得非常重要。823K,250MPa,30min条件下制备样品的相对密度达到97%,但样品表面容易产生裂纹。经823K,6MPa,10min完全反应的Mg2Si在1023K,20MPa,10min条件下进行二次烧结,获得了结构均匀、相对密度为98%的Mg2Si块体热电材料。

Magnesium silicide (Mg2Si) is one kind of narrow-band-gap n-type semiconductor, and is a promising environmentally friendly thermoelectric material because of its high electrical conductivity and low thermal conductivity, and also because it is non-toxic and non-polluting. High-purity magnesium (Mg) and silicon (Si) powders were selected as the raw materials, and fabrication of the Mg2Si thermoelectric material was systematically explored using the spark plasma sintering technique. The densities of the specimens were tested, and the phases and microstructures of the specimen were analyzed by X-ray diffraction and field emission scanning electron microscope, respectively. The results show that the synthesis temperature for Mg and Si is 823 K, 30 min and excessive content of Mg is helpful for obtaining pure Mg2Si. The relative density can reach 97% when the sample is prepared under the conditions of 823 K, 250 MPa, 30 min, but cracks were found on the surface of the sample. The sample was prepared under the conditions of 823 K, 6 MPa, 10 min, and then re-sintering at 1 023 K, 20 MPa, 10 min Mg2Si bulk with fine structure and relative density of 98% was obtained.