Effects Of Rare Earth Doping On The Properties Of Mn-Zn Ferrites For Magnetic Stripes In Electromagnetic Heating System

Electromagnetic induction heating technology has many advantages,such as high thermal conversion efficiency,environmental protection,safety and easy control.It has been widely used in industry and daily life.Induction cooker is the specific application of electromagnetic induction heating technology.Its popularization not only greatly facilitates our life,but also improves the energy utilization of our daily cooking.At present,the energy efficiency of induction cooker is generally around 88%,and how to further improve the energy efficiency is a major problem.Magnetic strip is an indispensable parts of induction cooker,which affects the energy efficiency,safety and stability of induction cooker to a certain extent.The current material for magnetic strips is manganese-zinc ferrite?Mn-Zn ferrite?.In this thesis,the improvement of soft magnetic properties of Mn-Zn ferrite strip material by adding rare earth is studied.The Mn-Zn ferrites with Fe₂O₃:ZnO:MnO₂=52.5:12:35.5?molar ratio?was prepared by traditional ceramic oxidation method,and different rare earth oxides and traditional additives such as CaCO₃ and BiO₃ were added to the samples.The preparation of the materials and the effects of adding elements on its structure and properties were studied.The mechanism of adding rare earth elements effects was also analyzed.The main research contents and results are as follows:Firstly,Mn-Zn ferrites with the addition single-component of rare earth oxides La₂O₃,Yb₂O₃ or Sm₂O₃ were prepared.It was found that the addition of Sm₂O₃ has better effects.It can improve the microstructure homogeneity and greatly reduce the coercivity and magnetic loss.The samples with 0.01 wt.%Sm₂O₃ has the best magnetic properties.At room temperature of 25?,frequency of 20 kHz and magnetic field intensity of 100 mT,the amplitude permeability is 3.31k,the coercivity is 2.74 A/m,and the magnetic loss is 2.99W/kg.Secondly,The Mn-Zn ferrites with different contents of rare earth oxides Ce₂O₃,Sm₂O₃and CaCO₃ were prepared at different sintering temperatures.It is found that the grain size increases with the increase of sintering temperature or Ce₂O₃ content.The higher sintering temperature is,the higher the amplitude permeability of the sample is.The excessive addition of Sm₂O₃ sintering at 1350?could easily induce exaggerated grain growth,resulting in deteriorating the magnetic properties of the sample seriously.The samples prepared with different processes show different comprehensive properties.The sample sintered at 1350?with 0.01 wt.%Ce₂O₃+0.05 wt.%CaCO₃ addition has an amplitude permeability of 4.11k,coercivity of 10.55 A/m,and magnetic loss of 12.05 W/kg.The sample sintered at 1300?with 0.01 wt.%Sm₂O₃+0.03 wt.%CaCO₃ addition has an amplitude permeability of 2.38k,coercivity of 2.92 A/m,and magnetic loss of 3.20 W/kg.The sample sintered at 1350?with0.05 wt.%Sm₂O₃+0.03 wt.%CaCO₃ addition has an amplitude permeability of 3.88k,coercivity of 13.047 A/m and magnetic loss of 16.01 W/kg.Finally,the Mn-Zn ferrites with Sm₂O₃+CaCO₃+Bi₂O₃ multi-component addition were designed and prepared based on orthogonal experiment.The results show that multi-component addition is beneficial to increase the amplitude permeability of the samples.For the samples with low total amount of combined addition,the initial permeability is higher,and coercivity and magnetic loss is lower at the same frequency.For the sample with 0.01 wt.%additions of Sm₂O₃,CaCO₃ and Bi₂O₃,its initial permeability is about 2500,and has amplitude permeability of 4.27k,coercivity of 4.44 A/m and magnetic loss of 4.86 W/kg.The sample with Sm₂O₃,CaCO₃ and Bi₂O₃ additions of 0.05 wt.%,0.01 wt.%and 0.05 wt.%,respectively,exhibits the initial permeability of about 2250,the amplitude permeability of5.30k,coercivity of 6.97 A/m and magnetic loss of 7.64 W/kg.The results show that the addition of rare earth oxide is beneficial to improve the properties of Mn-Zn ferrite materials and meet the application requirements of induction cooker.The conclusions of this thesis can be used to guide the production of Mn-Zn ferrite magnetic strips for electromagnetic heating.The present work have positive significance for the popularization and utilization of electromagnetic heating technology with energy saving and emission reduction.