Regular Article

Interfacial reactions between impurities and slag onset of Si purification by slag addition

¹ School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China
² Jiangsu Key Laboratory of Advanced Metallic Materials, School of Materials Science and Engineering, Southeast University, Nanjing 211189, China
³ State Key Lab of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, China

^* e-mail: zhanglifeng@ysu.edu.cn

Received: 12 August 2021
Accepted: 29 November 2021

Abstract

The interfacial reactions between impurities (Al and Ti) and slag onset of Si purification by 51 mol% SiO₂–34 mol% CaO–15 mol% MgO slag addition were studied to enhance impurity removal efficiency from Si. The Al distribution behavior at the Si/Slag interface was investigated; a short reaction time (10 s) resulted in the formation of successive SiO₂–CaO–MgO–Al₂O₃ layers in the slag with a thickness of 10 µm; increasing the reaction time (60 s) resulted in the entire ternary slag being changed into SiO₂–CaO–MgO–Al₂O₃ quaternary slag due to the diffusion of Al₂O₃. It was shown that the highest impurity removal rate of Al could be achieved at the onset of the slag refining process. Based on the Ti distribution at the Si/slag interface, the slag refinement with 51 mol% SiO₂–34 mol% CaO–15 mol% MgO had no effect on Ti removal.