Studies On Formulations Of M-type Permanent Magnetic Strontium Ferrites

Permanent magnetic ferrites are widely used in automobiles,household appliances,computers,electric tools and toys etc.In recent years,with continuous development of these areas,the yield and output value of permanent magnetic ferrites have been increasing in our country and the annual growth rate is roughly 10%.This thesis studies on the process and formulation of M-type permanent magnetic strontium ferrites.The main works and conclusions are as follow:?1?The optimal process parameters are 1:1.4 for the additive ratio of powder and water,22 h for the ball grinding and 0.6wt % of calcium gluconate.?2?Based on investigation of the effect of conventional secondary additives?SiO₂,CaCO₃,H₃BO₃,Al₂O₃,Cr₂O₃?on the performances of samples,the optimal recipe for secondary composite additives is 0.2wt% SiO₂,0.8wt% CaCO₃,0.4wt% H₃BO₃,0.4wt% Al₂O₃ and 0.6wt% Cr₂O₃.The performances of samples can reach Br=412.7 mT,Hcj=336.7 kA/m,Hcb=308.9 kA/m and?BH?max =32.15 kJ/m³.?3?Effects of rare earth element La and transition metal element Co on the performances of samples are studied and the superior recipe is 1.0wt% La₂O₃,1.0wt% Co₂O₃,0.2wt% SiO₂,0.8wt% CaCO₃,0.4wt% Al₂O₃,0.4wt% H₃BO₃ and 0.6wt% Cr₂O₃.The performances can achieve Br=406.7 mT,Hcj=390.5 kA/m,Hcb=314.7 kA/m and?BH?max=32.23 kJ/m³.?4?The substitution of La and Co for M-type permanent magnetic strontium ferrites Sr1-xLaxFe12-xCoxO19 was investigated.The proper La and Co substitution?x=0.1⁰.3?matains the single phase of the M-type strontium ferrites.Adding more La and Co?x>0.3?,?-Fe₂O₃ and CoFe2O4 appear.As La and Co substitution amount increases from 0 to 0.5,the Ms increases at first and then decreases and finally increases again.However,the Hc of samples gradually increases.The M?ssbauer spectra indicate that Co3+ substitutes sublattice positions of 4f2 and 2a of M-type strontium ferrites.