Research On Preparation Techniques Of Sr M Permanent Ferrite Based On Different Raw Materials

As a large producer of permanent ferrites,China is rich in iron ore resources.But the iron-red required for the preparation of permanent ferrites mainly depends on imports.There is a large gap between the product performance and the international advanced level.Therefore,the thesis work carries out research on the preparation technology of SrM permanent ferrites based on different raw material systems to investigate the influence of key technologies such as ion substitution,additives and preparation process on the magnetoelectric properties of SrM permanent ferrites.On the one hand,the low-cost and efficient utilization of indigenous iron ore is realized,and on the other hand,the independent development of high-performance SrM permanent ferrite materials is achieved.Firstly,SrM permanent ferrite was prepared based on the iron ore raw material system.Through XRF and XPS analysis and characterization,it is clear that the main components of iron ore raw materials are TFe≥69%,SiO₂≤0.40%,Al₂O₃≤0.58%;then optimized the iron deficiency formulation of SrM permanent ferrite,and it is concluded that when the iron deficiency is in the range of 0～1.0,with the increase of iron deficiency,the B_r,H_cb,H_cjandρof SrM permanent ferrite first increases and then decreases;The increase of pre-sintering temperature can improve the B_r andρ,but H_cb and H_cj will decreases;use CaCO₃,SiO₂ and H₃BO₃ additives to regulate the grain boundary characteristics,in which suitable CaCO₃ additives can increase B_r,（BH）_max andρ,suitable SiO₂ additives can increase the B_r,H_cb,H_cj,（BH）_max andρ,and suitable H₃BO₃ additives can increase H_cb and H_cj;the increased of sintering temperature promote sintering densification,resulted in an increase in B_r and（BH）_max.The final optimized properties of SrM permanent ferrite based on the iron ore raw material system are B_r=3828 Gs,H_cb=3577 Oe,H_cj=3914 Oe,（BH）_max=3.50 MG·Oe,andρ=149.3Ω·m.Then SrM permanent ferrite was prepared based on the purified iron-red raw material system.The main components of iron-red were TFe≥74%and SiO₂≤0.02%;the effects of La,Ca and Co ion substitution,pre-sintering and sintering temperature on the performance of SrM permanent ferrites were compared and analyzed by DOE.In five factors,the La ion substitution,pre-sintering and sintering temperature have the most significant effects on the magnetic properties of SrM permanent ferrites;when the Fe deficiency is in the range of 0～1.20,the B_r,（BH）_max andρof SrM permanent ferrite increased with the increase of Fe content;the increase of La ion substitution can increase the B_r,（BH）_max,but H_cb,H_cj andρfirst increase and then decrease;the increase of pre-sintering temperature can improve the H_cb and H_cj of the SrM permanent ferrite;the extension of the secondary ball milling time can increases the powder activity and improve the B_r and（BH）_max of the SrM permanent ferrite;the increase of sintering temperature can improve B_r,（BH）_max andρof the SrM permanent ferrite but reduced H_c.the final optimized properties of SrM permanent ferrite based on the iron-red raw material system are B_r=4201 Gs,H_cb=3867 Oe,H_cj=4371 Oe,（BH）_max=4.28 MG·Oe,andρ=276.3Ω·m.