Equilibrium Phase Relations In The Tetrahedron Phase Diagram For CaO-SiO₂-10%La₂O₃-Nb₂O₅ System

Bayan Obo tailings are rich in niobium and rare earth resources,in the pyrometallurgy extraction process of niobium and rare earth resources from Bayan Obo tailings,a complex slag is formed.Phase diagram is the most intuitive tool to study the properties of metallurgical slags.However,the phase diagram of correlative slag system has not been drawn up to now.So the uncertainty of thermodynamic property of correlative slag system restricts the research and development of recovery and utilization technology of niobium and rare earth resources from Bayan Obo tailings.In this paper,based on the comprehensive utilization of the resources of the tailings in Bayan Obo,according to the composition of the tailings in Bayan Obo,the CaO-SiO₂-10%La₂O₃-Nb₂O₅ system was selected as the study of the slag system.The phase equilibrium relationship was determined experimentally at 1200? and 1000? using the quenched technique followed by XRD and SEM-EDS analysis,high temperature phase composition of CaO-SiO₂-10%La₂O₃-Nb₂O₅ system was investigated.The independent tetrahedral region of CaO-SiO₂-La₂O₃-Nb₂O₅ quaternary slag phase diagram was drawn.Under the experimental conditions,the conclusion as follows:?1?The equilibrium solid phases of CaO-SiO₂-10%La₂O₃-Nb₂O₅ slag system at 1200?are SiO₂,CaO-Nb₂O₅,?Ca,La,Nb?O,2CaO·Nb₂O₅ and?Ca,Si,Nb?O.?2?The equilibrium solid phases of CaO-SiO₂-10%La₂O₃-Nb₂O₅ slag system at 1200?are SiO₂,Nb₂O₅,CaO-Nb₂O₅,2CaO·Nb₂O₅,CaO-SiO₂,La₂O₃-6Nb₂O₅,?Ca,Si,La?O,?Ca,La Nb?O and?Ca,Si,Nb?O.?3?The compositions of?Ca,La,Nb?O and?Ca,Si,Nb?O are Cao.92Nb1.46La1.62O7 and 10CaO·Nb₂O₅-6SiO₂.?4?According to the equilibrium results of CaO-SiO₂-10%La₂O₃-Nb₂O₅ system at 1200? and 1000?,the separation of five independent tetrahedral regions in the tetrahedral phase diagram are determined:???SiO₂—CaO·Nb₂O₅—?Ca,Si,La?O—Cao.92Nb1.46La1.62O7;???SiO₂—CaO·Nb₂O₅—La₂O₃·6Nb₂O₅—Nb₂O₅;???2CaO·Nb₂O₅—CaO·SiO₂—Ca0.92Nb 1.46Lai.62O7—10CaO·Nb₂O₅·6SiO₂;???SiO₂—CaO·SiO₂—CaO·Nb₂O₅—?Ca,Si,La?O;???CaO·Nb₂O₅—2CaO·Nb₂O₅—CaO·SiO₂—Cao.92Nb1.46La1.62O7?...