元素掺杂对合成β-FeSi_2的影响

Effect of elements-doping on synthesis of β-FeSi_2

采用燃烧合成热压工艺制备热电材料β-FeSi2,研究Cu、Al元素含量对合成β-FeSi2的影响。利用X射线衍射仪和扫描电镜分析合成的铁硅化合物的相组成及其微观结构形貌。结果表明:在共析反应α→β+Si生成β-FeSi2的过程中,随Cu含量增加,反应速度提高。当掺入原子分数为0.8%的Cu时,α相完全转变为β相;铝的掺入可以提高原始粉料利用率,且铝对α-Fe2Si5向β-FeSi2转变的促进作用不太明显。为了避免铝的过多掺入,在掺入2%Al的同时掺入0.2%Cu,α-Fe2Si5完全转变为β-FeSi2,β相的峰值达到最高。热压烧结试样的断口形貌显示:α-Fe2Si5在共析反应中生成了尺寸均匀的β-FeSi2小颗粒,Si单质弥散分布于其周围,整个产物呈疏松多孔状。

Thermoelectric material fl-FeSi2 was prepared by the method of combustion synthesis- hot pressing. Effects of content of Cu, A1 on the synthesis of fl-FeSi2 were studied. The phase composition and mierostructure of Fe-Si intermetallics were investigated by means of X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results show that the reaction rate increases with the increase of Cu content, and when atom fraction of doped Cu is 0.8%, a phase is completely transformed into fl phase. A1 doping can improve the utilization of the original powder, and the effect of doped A1 is not obviously in the process of a-β＋Si. In order to avoid excessive AI, 2% A1 and 0.2% Cu was added in original powder at the same time, which leads the a-Fe2Si5 transforming into β-FeSi2 completely, and the hot pressed samples achieving the highest peak of the fl phase. The fracture morphologies of hot pressed samples show that the generated small particles of uniform size are generated in the eutectoid reaction, and the Si particles disperse around it, and the samples are loose and porous.