Research On The Formulation And Preparation Process Of YIG Ferrite

YIG ferrites have been applied extensively in microwave devices in different frequency,due to its adjustable saturation magnetization 4?Ms,small ferromagnetic resonanace linewidth ΔH,low dielectric loss and controllable Curie temperature Tc.The representative structure lay the foundation to research YIG-based ferrites.With the increasing complexity of the microwave devices,the higher demands were put forward to the YIG ferrites used in them,thus,it is significant to satisfy the demand by modifying the YIG ferrites properties.In this proposition,the YIG ferrites have been studied via formula and process.Particularly,the thermomagnetization characteristics and microwave performances were analyzed deeply.The YIG ferrites were prepared by traditional oxide ceramics process.The influences of variational mill medium,additive,sintering temperature and various ions-substitutions on microstructure,magnetic properties and microwave performances for YIG ferrites are studied.The main contents and consequences reveal as follows:1.The saturation magnetization 4?Ms,residual magnetic induction Br and resistivity ? of YIG milled by ZrO2 media are all larger than the specimen milled by Iron media,meanwhile,the coercivity Hc is lower.Bi2O3 contributes to promote solid phase reaction and raise density.BaTiO3 additive enhances the dielectric constant ?r and reduces the loss angle tangent tan??.The appropriate enhancement of sintering temperature helps to raise densification and reduce Hc.2.The properties of YIG ferrites were studied through ions substitution,the results as follow: Ni2+ substituted Y2.3Ca0.7Zr0.3V0.2Nix Fe4.5-x O12-x/2 samples exist YFeO3 phase,leads to the reduction of 4?Ms and Br.Besides,density and Hc increase and grain size decreases.The introduction of Cu2+ ions low the Y2.3Ca0.7Zr0.3V0.2Nix Fe4.5-xO12-x/2 samples sintering temperature obviously.When x≥0.2 the YFeO3 phase leads to the decrease of 4?Ms and Br,while density and Hc increase.Meanwhile,4?Ms and Br increase firstly and then decrease with the increasing temperature at the same substitution contents.The lattice constants of Y2.6-x Ca0.4+xFe4.8-x V0.2ZrxO12 become larger gradually with the rise of Zr4+ substitution amounts.At the same sintering temperature,Br and density decrease continuously,while Hc has converse trend.However,the 4?Ms increases from x=0.0 to 0.4 and then reduces after 0.4.In addition,when substitution is invariable,with the increase of sintering temperature 4?Ms change large firstly and then decrease.Density decreases slightly in a range of 0.0~0.3 and hardly varies after 0.3.With increasing Sn4+ substitution contents,the 4?Ms of Y3-x CaxFe5-x Snx O12 increases gradually while Br changes tinily.Besides,at the same substitution contents,4?Ms,Br and density increase firstly then decrease,while Hc has converse regulation.Moreover,based on Néel molecular filed theory,the molecular filed coefficients ?aa,?dd and ?ad=?ad were computed by non-linear fitting method,meanwhile,the calculated magnetic moment verse temperature curves are coincided well with the that of experiment in the temperature range from 1.8 to 400 K.According to the results,the Curie temperature Tc decrease continuously leaded by the reduction of coefficients ?ad=?ad with the increase of Sn4+ substitution contents.Apart from this,the ferromagnetic resonance linewidth ΔH decreases to the minimum of 3.36kA/m and then increases slightly.The magneto crystalline anisotropy K1 was acquired via the law of approach to 4?Ms,and the leading factors of ΔH was recognized based on spin wave theory.3.The effects of SnO2-V2O5 combined substitutions on magnetic properties of Y3-x-2yCax+2yFe5-x-y SnxVyO12 ferrites was discussed through the orthogonal experimental design routine.The results shown as follow: Bs and Br are mainly effected by V5+ ions substitution;the Sn4+ ions substitution help to decrease Hc effectively;the density is lagely influenced by V5+ ions substitution.Finally,the optimized formula is x=0.4,y=0.03,the superior properties were obtained at sintering temperature 1420 ℃,the specific parameters are: Bs=190mT,Br=112mT,d=5.12g/cm3,Hc=17A/m.