Element migration and phase distribution characteristics during crystallization of rare earth phase in rare earth slag

The crystallization experiment of molten rare earth (RE) slag under different cooling rates was carried out. The characteristics of element migration and phase distribution during RE phase crystallization were studied by using different equipment. The experimental results show that there are two RE phases in the RE slag, namely (Ca, Ce, La)5(SiO4)6F and (Ca,Ce,La,Mg)3(Ti,Al,Nb)2O7. During the cooling crystallization process of molten RE slag, Ca and P elements in the RE phase of (Ca,Ce,La)5(SiO4)6F migrate from inside to outside, and finally gather at the outer edge of the phase to form phase Ca3(PO4)2. The RE phase (Ca,Ce,La)5(SiO4)6F is distributed inside the furnace-cooled slag, and the RE phase (Ca,Ce,La,Mg)3(Ti,Al,Nb)2O7is distributed in the surface layer of the furnace-cooled slag. And based on the phase distribution characteristics, the central hollowing method is proposed to realize the preliminary enrichment of valuable elements Ti, Nb and RE in RE slag.