Study On Magnetic Properties And Microstructure Of M-type Ferrites Sr_1-xA_xFe_12-yCo_yO₁₉?A= Ca,La?

M-type hexagonal ferrites(BaFe12O19,SrFe12O19)have widely used in permanent magnets,microwave devices and magnetic recording because of the relatively low price,high coercive,large magnetocrystalline anisotropy field and excellent chemical stability.All samples of this dissertation were prepared by solid state reaction method,the magnetic powders and magnet were tested by XRD(CuKa,? = 1.5418 A).The microstructure of the magnet was observed by SEM.The magnetic properties of magnet were tested by demagnetization curve B-H.The influence of Ca2+ and La3+-Co2+ content on permanent magnetic properties(Br,Hcb,Hcj and(BH)max)was investigated.The main contents are as follows:1.Sr1-xCaxFe12O19 magnetic powders and magnets were prepared by solid state method,Ca2 replaces Sr2+ of SrFe12O19.The influence of Ca2+ content on the magnetic properties and microstructure were studied.Within content range of 0.00 ? x ? 0.30,the results confirmed that the lattice constant c decreased with the increase of Ca2+ content,and the shape of grains showed regular hexagonal structure.Br,Hcb,and Hcj increased firstly and then decreased with the increase of Ca2+ content.Among them,Br increased 175 Gs and Hcj increased 125 Oe.2.Based on the first step,selected the best Ca2+ content.The Sr2+ and Fe3+ in SrM were replaced by La3+-Co2+.Within content range of 0.00 ?y ? 0.24,the lattice constant c decreased with the increase of La3+-Co2+ content,and the shape of grains showed regular hexagonal structure.The Br,Hcb,Hcj and(BH)max of the magnet increased firstly and then decreased with the increasing content of La3+-Co2+.Among them,Br increased 184 Gs,Hcj increased 1001 Oe,Hcb increased 511 Oe,(BH)max improved 0.52 MGOe.3.On the basis of the previous two steps,selected the best La3+-Co2+ content.The variation range of Ca2+ content was narrowed,and explored the influence of Ca2+content on the magnetic properties of SrM.Within the Ca2+ content range of 0.22<x<0.28,the Br,Hcb and(BH)max values of the magnet increased firstly and then decreased with the increase of the Ca2+ content.Furthermore,the value of Hcj decreased slightly.Among them,Br increased 24 Gs,Hcb improved about 68 Oe,Hcj reduced by 68 Oe,(BH)max improved 0.071 MGOe.4.Based on the previous three steps,selected the best Ca2+ content.Narrowed,the range of La3+-Co2+ content perfectly utilized.The influence of La3+-Co2+ content on the magnetic properties of SrM was investigated.Within the La3+-Co2+ content range of 0.17?y0?.23,the Br,Hcb and(BH)max values increased firstly and then decreased with the increase of La3+-Co2+ content,but the Hcj value of the magnet decreased slightly.Among them,Br increased 28 Gs,Hcb improved about 50 Oe,Hcj reduced by 10 Oe,(BH)max increased 0.069 MGOe.5.Through the above four steps,the optimized Ca2+ and La3+-Co2+ content have been obtained.We selected the best formula and explored the effects of additive SrCO3 and La2O3 on the magnetic properties.The results showed that all values of Br,Hcb,Hcj and(BH)max were increased firstly then decreased with the increase of SrCO3 content.Compared with non-addition SrCO3,Br increased 30 Gs,Hcb improved about 48 Oe,Hcj increased 142 Oe,(BH)max increased 0.07 MGOe.The XRD of the magnet indicates that the sample shows a single M-type ferrite phase,and the orientation of the magnet was very good.In addition,the values of the Rr,Hcb,Hcj and(BH)max increased firstly,then decreased with the increase of La2O3 content.Compared with non-addition La2O3,Br increased 20 Gs,Hcb increased 19 Oe,Hcj increased 229 Oe,(BH)max improved 0.047 MGOe.