Development Of Communications Devices From Rare Earth Doped Ni-Zn Ferrites

In this dissertation,the properties of Ni_0.5Zn_0.5Fe₂O₄ ferrite were improved by doping modification and processing optimization.Microstrip slot antennas and inductive couplers were designed through using electromagnetic simulation software CST STUDIO SUITE 2014.The performances of the prepared ferrite materials in the application of such devices were evaluated.?1?Sm-doped and Ho-doped Ni-Zn ferrites were prepared by solid state sintering.Both Sm³⁺and Ho³⁺can increase the Curie temperature and decrease the dieletric loss of the prepared ferrites.But the doping of Ho³⁺increased the Curie temperature more significantly.?2?Ni-Zn ferrites prepared by molten salt method can effectively reduce the presintering and sintering temperature.And the final,sintered ceramics become denser and more uniform in grain size.The spinel phase can be formed by molten salt method at a low temperature of 300?.Moreover,the final sintering temperature can be reduced?about 50??,compared with that by the solid sintering method.?3?Ho³⁺/Co²⁺and Ce³⁺/Co²⁺doped Ni-Zn ferrites were prepared by molten salt method.The Curie temperature of Ni_0.5-xZn_0.5Ho_0.02Co_xFe_1.98O₄ samples doped with Ho³⁺/Co²⁺increased with the increase of doping amount,reaching the maximum value when the content of Co was x=0.015.The dielectric loss of the Ni-Zn ferrite obviously decreased when Ho³⁺/Co²⁺ions were doped into the ferrites.And the Ce³⁺/Co²⁺co-doping into the Ni-Zn ferrites can effectively inhibit the reduction of density and saturation magnetization caused by doping Ce³⁺and Co²⁺independently.The Ce³⁺/Co²⁺co-doping can significantly increase the Curie temperature of the obtained Ni_0.4Zn_0.5Co_0.1Ce_xFe_2-xO₄.And the cut-off frequency of the prepared materials would be increased by co-doping of Ce³⁺and Co²⁺.?4?Microstrip slot antenna and inductive coupler were designed by electromagnetic simulation software CST STUDIO SUITE 2014.The dielectric loss of the ferrite devices obviously decreased when Ho³⁺/Co²⁺ions were co-doped into the Ni_0.5-xZn_0.5Ho_0.02Co_xFe_1.98O₄.When the doping amount of Co²⁺was x=0.015,the microstrip slot antenna has higher transmittance and resonance frequency than that of Ni_0.5Zn_0.5Fe₂O₄ devices.The applicable frequency of the coupling units was significantly enhanced from 10 to 103 MHz after the co-doping of Ce³⁺and Co²⁺than that of Ni_0.5Zn_0.5Fe₂O₄.