Effect Of La₂O₃ On Conductivity Of SiO₂-CaO-Al₂O₃-MgO Melt At High Temperature

Since its exploitation and utilization,Bayan-Obo Mine has been dominated by iron ore for a long time,giving consideration to Rare Earth,resulting in low utilization rate of Rare Earth resources,and a large number of Rare Earth are piled up in the tailings.The production of Rare Earth glass ceramics from Bayan-Obo Rare Earth tailings can not only solve the waste and pollution of Rare Earth resources but also create economic value.The melting process of electric kiln is an important segment in the production of glass and ceramics.In this segment,the electrical conductivity affects the melting effect of melt,and then affects the temperature field distribution and energy consumption of electric kiln.Therefore,the study of the effect of Rare Earth on electrical conductivity has an important guiding role in the optimization of production process,and provides a theoretical basis for understanding the mechanism of Rare Earth on the physical properties of glass ceramic melt.The basic composition of glass ceramics is silicon aluminate.In this thesis,SiO₂-CaO-Al₂O₃-MgO-La₂O₃five-element system is designed as the research object to study the influence of La₂O₃on the electrical conductivity of silicon aluminate high-temperature melt.The effect of La₂O₃on melt conductivity was analyzed by infrared spectroscopy,and the typical silicoaluminate conductivity model was adaptively modified.Firstly,the influence of La₂O₃content on the conductivity of SiO₂-CaO-Al₂O₃-MgO melt was studied by four-electrode method,and the effect of La₂O₃on the melt structure was analyzed by infrared spectroscopy.The results show that the melt conductivity increases with the increase of temperature.At the same temperature,the melt conductivity increases with the increase of La₂O₃content,and the conductivity and La₂O₃content showed a linear trend.La₂O₃is a network modifier in the silicon aluminate melt.With the increase of La₂O₃content,the melt structure of[SiO₄]^4-tetrahedral depolymerization tends to simplify,the number of free moving ions in the melt increases,and the conductivity of the melt increases.The effect of La₂O₃on the conductivity of SiO₂-CaO-Al₂O₃-MgO high temperature melt under different CaO/SiO₂ratio and different Al₂O₃content was further studied.The results show that the melt conductivity increases with the increase of CaO/SiO₂ratio,and when the CaO/SiO₂ratio is low,the increase of La₂O₃content makes the conductivity-temperature curve turn and the slope of the curve changes greatly,and La₂O₃has a greater influence on the melt conductivity.The conductivity of the melt decreases with the increase of Al₂O₃content,and the conductivity-temperature curve becomes more dispersed and the slope changes more when Al₂O₃content is low,and La₂O₃has a greater influence on the conductivity of the melt.Infrared spectrum analysis shows,when the CaO/SiO₂ratio and Al₂O₃content are low,with the increase of La₂O₃content,the band center of[SiO₄]^4-tetrahedron shifts to the direction of low wave and the wave number changes more,meanwhile,the change of Q²and Q³absorption peaks is more obvious,and the depolymerization of La₂O₃on[SiO₄]^4-tetrahedron is stronger.The influence of La₂O₃on the conductivity of melt is greater.The lower the CaO/SiO₂ratio and Al₂O₃content,the more obvious the influence of La₂O₃content on the activation energy of electrical conductivity.Finally,the conductivity model of the system was established based on the Arrhenius formula and modified optical basicity.The coefficients m and n of the conductivity model parameters were modified in the temperature range of 1698～1823K combined with the conductivity data of some samples.The modified coefficients m and n were 6.0603×10^-5and-2.1294.The maximum error is 30.05%,the minimum error is 0.05%,and the average error is 6.54%.The model can well predict the conductivity behavior of silicon aluminate melt containing La₂O₃with composition and temperature.The relationship between conductivity and viscosity was established as:lnη=-5.00-2.14lnσ.