Indexed by:Journal Papers

Date of Publication:2015-09-15

Journal:JOURNAL OF CRYSTAL GROWTH

Included Journals:SCIE、EI、Scopus

Volume:426

Page Number:202-207

ISSN No.:0022-0248

Key Words:Directional solidification; Upgraded metallurgical-grade silicon; Envelopment; Removal; CaO particle

Abstract:Directional solidification is often used to remove metallic impurity in the photovoltaic industry for the low equilibrium distribution coefficient between solid and melt. However, in our present experiments, compared with other impurities, the removal of calcium is variable at the low height of ingot, which is caused by the existence of insoluble CaO particle. CaO exists as insoluble particle in the feedstock. During directional solidification stage, CaO motions with the melt convection, and it is likely to envelop in solid. Consequently, the content of calcium is relatively high if many CaO particles are just contained, which is verified by the analysis of SEM-EDS. In a word, the removal efficiency depends upon the chemical state of calcium. The reason why CaO exists is studied, and the envelopment of the particle is mainly discussed by means of thermodynamics, especially on gravitational force, repulsive force, and drag force. (C) 2015 Elsevier B.A. All rights reserved.