TY  - JOUR
AU  - Zhu, Mengyi
AU  - Yue, Shengying
AU  - Wu, Guixuan
AU  - Tang, Kai
AU  - Xu, Yijiang
AU  - Safarian, Jafar
TI  - P removal from Si by Si-Ca-Al alloying-leaching refining: Effect of Al and the CaAl2Si2 phase
JO  - Separation and purification technology
VL  - 271
SN  - 1383-5866
CY  - Amsterdam [u.a.]
PB  - Elsevier Science
M1  - FZJ-2021-05600
SP  - 118675 -
PY  - 2021
AB  - Phosphorus (P) is a critical impurity in metallurgical-grade Si that needed to be removed for solar-grade Si production. The Si-Ca-Al-P system is one of the most crucial alloy systems for Si refining, where P can be separated by either the Si-Al solvent refining or the Si-Ca alloying-leaching process. In this work, a series of Si-Ca-Al alloys were obtained to investigate the role of alloy composition and the CaAl2Si2 phase in P segregation and separation. The used alumina crucible led to heavy Al contamination and resulted in unexpected Si-Ca-Al alloy compositions. CaAl2Si2 and CaSi2 were found as the main precipitates, and relatively higher P content was detected in the CaAl2Si2 phase. Leaching experiments indicate that P removal degree increases with increasing Ca/Al ratio and increasing total alloying amount (Ca + Al). Effects of alloy composition were further analyzed by statistical methods, which indicates Ca firmly plays a strong, positive, and monotonic role in P removal while no strong attraction between Al and P. Theoretical P removal model for the Si-Ca-Al system was established and in good agreement with measured results. Interaction coefficients of Ca and Al to P were fitted as and , which further confirms Ca is the essential driving force for P segregation. Finally, the possibility of P solid solution formation was verified by first-principle simulations that both CaAl2Si2 and CaSi2 are able to dissolve P, especially through the Si site, but the CaAl2Si2 phase is more favourable for P dissolution than CaSi2, which explains the reason of the often detected high P content in CaAl2Si2.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000656879100003
DO  - DOI:10.1016/j.seppur.2021.118675
UR  - https://juser.fz-juelich.de/record/904030
ER  -