Abstract:In order to reveal directional crystallization rules of niobium minerals in Nb2O5-Al2O3-MgO-Na2O-CaO-SiO2 multi-component slag system, the influence of calcium-silicon ratio (CaO/SiO2), Nb2O5 content and temperature on phase balance of slag was investigated by the high temperature equilibrium, cold quenching, SEM-EDS/XRD/EMPA method. A dominant phase diagram for the crystallization of niobium-containing minerals was constructed. The results show that three niobium phases are found in the system, it is Ca2Nb2O7, Ca(14-x)Nb(2+x)Si8O(35+1.5x) and 3CaO?MgO?Nb2O5 respectively; Niobium is enriched in the liquid phase first, and compared with the gangue components, the niobium-containing solid phase is the later precipitated phase; With the increase of CaO/SiO2, the dominant interval of the niobium-containing solid phase changes from Ca2Nb2O7 phase to Ca(14-x)Nb(2+x)Si8O(35+1.5x) phase, and then to 4CaO?MgO?Nb2O5 phase. The dominant crystallization range of Ca2Nb2O7 phase is temperature at 1 050—1 200 ℃ and CaO/SiO2=0.8—1.2. The intercalation mass concentration of Nb2O5 in the Ca(14-x)Nb(2+x)Si8O(35+1.5x) phase is between 18.5% and 19.5%.