Removal of Phosphorus in Metallurgical Silicon by Rare Earth Elements

Abstract

Removal of phosphorus in metallurgical silicon is one of the crucial steps for the production of SoG-Si feedstock. The possibility of doping rare earth elements for phosphorus removal has in this work been studied both theoretically and experimentally. Thermochemical properties of Ce and Pr monophosphides have first been estimated by ab initio thermodynamic simulations based on density functional theory and the direct phonon method. The reliability of the first principles calculations was assessed by coupling with the phase diagram data of the Pr-P system. Equilibrium calculations confirmed the existence of stable rare earth monophosphides in solid silicon. Experimental investigations were then carried out, employing a high temperature resistance furnace. The Ce-doped silicon samples were examined by EPMA and ICP analysis. The efficiency of phosphorus removal by means of rare earth doping was discussed in detail in the paper.

Effects of La2O3 Addition into CaO-SiO2 Slag: Structural Evolution and Impurity Separation from Si-Sn Alloy

“…[35] that the increasing concentration of element with negative e P Me value can decrease the P segregation coefficient and, therefore, promote the impurity removal in acid leaching. The value of e P Ca ¼ À14:6 measured by Shimpo et al [65] at 1723 K (1450°C) [65] well supports the above explanation and the reported low Gibbs energy of formation of the lanthanide monophosphides [66] also implies the promoted P segregation in the slag-treated alloy. Thus, it is expected that the increasing slag basicity results in higher Ca and La contents in the metal phase, which further promotes the P segregation and benefits its removal in acid leaching.…”

Novel Approach for the Simultaneous Recovery of Nd from Nd2O3-Containing Slag and the Preparation of High-Purity Si

“…39 Si−REE solvents can also be used to purify Si. Tang et al 40 found that the addition of REEs can enhance the removal of P from Si with hydro-metallurgical treatment. Xi et al 41 reviewed the removal impurities from Si using hydrometallurgical technologies.…”