Mechanism of Direct Electrolytic Reduction of Solid SiO2 to Si in Molten CaCl2
Mechanism of Direct Electrolytic Reduction of Solid SiO2 to Si in Molten CaCl2
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DOI：
10.1149/1.1864453
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发表时间：
2005-04
影响因子：
3.9
通讯作者：
K. Yasuda;T. Nohira;K. Amezawa;Y. Ogata;Y. Ito
中科院分区：
文献类型：
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作者：
K. Yasuda;T. Nohira;K. Amezawa;Y. Ogata;Y. Ito
研究了SiO 2 在熔融CaCl 2 中直接电解还原的机理。对通过 SiO 2 接触电极在 1.10 V（相对于 Ca 2 + /Ca）、1123 K 下恒电位电解 1 小时制备的 Si 进行了形态和晶体学研究。X 射线衍射证实无定形 SiO 2 被还原为结晶 Si。从扫描电子显微镜(SEM)和能量色散X射线结果证明，Si柱垂直于Si和SiO 2 之间的反应界面形成，并且柱之间形成空隙。通过场发射SEM观察发现，Si柱基本上具有六棱柱形和堆叠结构。透射电子显微镜和电子衍射结果表明，Si柱是具有垂直于柱轴的{111}双晶面的单晶。据解释，非晶硅首先通过电化学还原形成，然后热转变为晶体硅。发现还原的速率决定步骤是O 2 - 在柱之间的空闲空间中的扩散。
The mechanism of direct electrolytic reduction of SiO 2 in molten CaCl 2 was studied. Morphological and crystallographic investigations were conducted on Si prepared by potentiostatic electrolysis of SiO 2 contacting electrode at 1.10 V (vs. Ca 2 + /Ca) for 1 h at 1123 K. X-ray diffraction confirmed that amorphous SiO 2 was reduced to crystalline Si. From scanning electron microscopy (SEM) and energy-dispersive X-ray results, it was proved that Si columns were formed perpendicular to the reaction interface between Si and SiO 2 and that vacant spaces were formed between the columns. It was found from field emission SEM observation that the Si column had basically a hexagonal prismatic and stacking structure. Transmission electron microscopy and electron diffraction results revealed that the Si column was a single crystal having {111} twin planes perpendicular to the axis of the column. It is explained that amorphous Si is first formed by electrochemical reduction and then thermally transformed to crystalline Si. The rate-determining step of the reduction was found to be O 2 - diffusion in the vacant space between the columns.