Solvent extraction of phosphorus from Si-Cu refining system with calcium addition

Enhanced removal of P from Si-Cu alloy was obtained by Ca addition. The effectiveness of Ca addition on the phase reconstruction and P gettering in Si-50 wt%Cu alloy was investigated. It was shown that the introduction of Ca can achieve the phase reconstruction of Si-50 wt%Cu alloy by the formation of CaCu2Si2 and CaCu11Si5 phases, which were precipitated in the Cu3Si phase. Dense P was found to homogeneously precipitated in the CaCu2Si2 phase, indicating that the increase in the amount of the CaCu2Si2 phase would collect more P. It was found that the extraction fraction of P was proportional to Ca content in Si-50 wt% Cu alloy. The removal fraction of P was increased from 27% to 82% when the Si-Cu system was doped with 5 wt% Ca. The thermodynamic analysis of P removal was investigated, showing that the Ca addition could effectively decrease the segregation coefficient of P between solid Si and the Si-Cu melt. It was concluded that Ca could be used as an impurity trapper to facilitate the P removal in the Si-Cu alloy.