Experimental Study On Phase Equilibrium Of Slag System Containing RE₂O₃ (RE=Sc, Gd, Sm)

Lanthanide elements and 17 kinds of elements such as Scandium and yttrium are rare earth elements.They are known as"industrial vitamins"and"the mother of new materials".As an important strategic resource,rare earth elements are used in chemical industry,metallurgy,nuclear energy and laser materials.High temperature superconductors,secondary batteries,and other fields are widely used.Rare earth elements are widely used in various application fields and are important strategic resources.In order to maintain the sustainable development of ecology and materials,from waste rich in rare earth elements,It is very urgent to recover rare earth from metallurgical slag and other low-grade secondary resources.The distribution of rare earth in slag is particularly important for the recovery of rare earth from high temperature smelting slag.The content of CaO,SiO₂ and Al₂O₃ in slag is very high,and it is the most commonly used flux in metallurgical industry,which has a great influence on the properties of slag system.Therefore,it is very necessary to study the phase diagram of slag system such as Sc₂O₃-CaO-Al₂O₃,CaO-SiO₂-Gd₂O₃ and CaO-SiO₂-Sm₂O₃.According to the high temperature metallurgical process of rare earth recovery from rare earth oxide slag system,the phase equilibrium relations of Sc₂O₃-CaO-Al₂O₃,CaO-SiO₂-Gd₂O₃ and CaO-SiO₂-Sm₂O₃ are studied in this paper.?1?Phase equilibria of the CaO-SiO₂-Gd₂O₃ slag system at 1773 K and 1873 K were investigated by characterizing equilibrated samples with electron probe microanalysis?EPMA?.Four three-phase equilibria and five two-phase equilibria are formed in the CaO-SiO₂-Gd₂O₃ ternary system at 1773K in argon atmosphere.While three three-phase equilibria,six two-phase equilibria and one liquid phase are presented in the system at1873K.The isothermal section of the phase diagram is thereafter constructed based on the experimental results.?2?The isothermal section of the Sc₂O₃-CaO-Al₂O₃ ternary system at 1773 K and1873 K was investigated.The 1773 K isothermal section consists of one liquid compound,six binary compounds and seven ternary compounds.At 1873 K,we found one liquid compound,five binary compounds and six ternary compounds to exist at the isothermal section.?3?The phase equilibria of CaO-SiO₂-Sm₂O₃ slag system at 1773 K and 1873 K were investigated.The phases formed in the CaO-SiO₂-Sm₂O₃ ternary system at 1773 K in argon are:four three-phase equilibria and five two-phase equilibria.The phases presented in the system at 1873 K are:four three-phase equilibria,seven two-phase equilibria.?4?the thermal analysis and in situ detection of CaO-SiO₂-Gd₂O₃ system were studied.The precipitation behavior of slag composition was affected by the addition of additive?B₂O₃?,and the temperature of liquid phase line and solid phase line was reduced.The above results provide the feasibility and recovery path of rare earth recovery,and also provide powerful experimental support for the supplement of thermodynamic data of rare earth oxides.