The Structural And Magnetic Properties Of NiZnCu And Ba Ferrites Prepared By Chemical Coprecipitation Method

Ferrite is a kind of widely-used non-metallic magnetic materials. With the virtue of finegrain and high activity, chemical coprecipitation method is well suitable for the preparation offerrite powders annealed at lower temperatures.In this thesis, NiZnCu and M-type Ba ferrite powders were prepared via chemicalcoprecipitation method, and the facts that affected their magnetic and crystalline properties werestudied.For NiZnCu ferrite powders, first, it was found that all the powder specimens exhibitsingle-phase structure no matter NaOH or Na₂CO₃was used as coprecipitator; the saturationmagnetization of specimens using NaOH as coprecipitator is lower than that of specimens usingNa₂CO₃as coprecipitator; and the growth of grains was hindered for the specimens usingNa₂CO₃as coprecipitator due to the existence of carbonates in the precursor powders. Second, asecond washing process introduced after drying can eliminate the impurity Na⁺ions effectuallyand thus help the formation of single-phase structure and the growth of grains. Third, themagnetic properties and crystal structures of Ni_0.25-2xLi_xCr_xCu_0.15Zn_0.6Fe₂O₄（x=0,0.01,0.02,0.03,0.04） are greatly affected by the content of Li-Cr substitutions, and it obtains a betteroverall performance when x=0.02.For M-type Ba ferrite powders with a nominal composition Ba（ZnTi）_xFe_12-2xO₁₉（x=0.0,0.2,0.6,1.0,1.4）, substitution of Zn²⁺and Ti⁴⁺ions can reduce the calcination temperature obviously;Saturation magnetization （Ms） and residual magnetization （Mr） obtained a maximum valuewhen x is about0.2. However, the coercivity is inversely related to x. It can be concluded thatthe samples with x=0.2⁰.6and a calcinated temperature at1000C presented the bestproperties.