【作者】 李伟；

【导师】 代波；

【作者基本信息】 西南科技大学 ， 材料科学与工程， 2024， 硕士

【摘要】 磁性材料是一类对外磁场有灵敏响应的特殊材料,对其研究和应用的历史悠久且广泛。其中,铁氧体材料的高电阻率使其在高频率下表现出低损耗的特性,同时铁氧体材料具有更广泛的应用频率、更强的耐腐蚀性、更实惠的价格和更高的耐热性以及良好的旋磁性能,因此,它被广泛应用于微波器件当中。在微波系统中,波导隔离器的应用十分广泛,它可以隔离输入和输出端口之间的信号,防止信号的反向传输,从而实现信号的定向传输和保护系统免受不必要的干扰。NiZn铁氧体是应用最广泛的铁氧体材料之一,可作为波导隔离器中的旋磁基片,所以制备出性能优异的NiZn铁氧体材料是提高波导隔离器性能的关键因素之一。本文首先对NiZn铁氧体中Ni²⁺与Zn²⁺的比例变化对其性能的影响进行了探索研究,通过常压烧结技术制备了Ni_xZn_1-xFe₂O₄（x=0.15、0.25、0.35、0.45、0.65、0.70、0.80和0.85）陶瓷基片。研究了不同Ni²⁺含量的NiZn铁氧体陶瓷基片微观结构和磁学性能。然后以热压烧结（HP）和放电等离子体烧结（SPS）的方式制备了Ni_0.65Zn_0.35Fe₂O₄陶瓷样品,并对样品的性能进行了测试分析。由于所制备NiZn铁氧体陶瓷尺寸的限制,最后选择常压烧结法制备的NiZn铁氧体陶瓷为旋磁材料,制备了波导隔离器,并测试了其电性能。研究表明:（1）常压烧结法制备的不同Ni²⁺含量的NiZn铁氧体陶瓷基片中,Ni_0.65Zn_0.35Fe₂O₄的饱和磁化强度最高可达78.68 emu/g,其4πM_s为4780 Gs,铁磁共振线宽（ΔH）为263 Oe。（2）热压烧结温度和保温时间会影响NiZn铁氧体陶瓷基片的旋磁性能,其中在热压烧结温度为1010℃时保温20 min制备的样品综合磁学性能最好,其饱和磁化强度为76.43 emu/g,4πM_s为5041G,铁磁共振线宽（ΔH）为352 Oe。（3）放电等离子体烧结温度、压力和保温时间都会影响NiZn铁氧体陶瓷基片的旋磁性能,其中当烧结温度为1150℃,保温时间为5 min,压力为1.5 t时制备的样品综合磁学性能最好,饱和磁化强度最高可达74.99 emu/g,4πM_s为4947 Gs。以常压烧结法制备的NiZn铁氧体陶瓷作为旋磁材料制作的波导隔离器可以在工作频率13.5～18.5GHz内稳定工作。更多还原

【Abstract】 Magnetic materials are a special class of materials that respond sensitively to external magnetic fields,with a long history of research and widespread applications.Among them,ferrite materials have high electrical resistivity,which results in low loss characteristics at high frequencies.Ferrite materials also have broader application frequencies,stronger corrosion resistance,more affordable prices,higher heat resistance,and good magnetization properties.Therefore,they are widely used in microwave devices.In microwave systems,the application of waveguide isolators is very common.They can isolate signals between the input and output ports,preventing reverse signal transmission,thereby achieving directional signal transmission and protecting the system from unnecessary interference.NiZn ferrite is one of the most widely used ferrite materials and can be used as the magnetized substrate in waveguide isolators.Therefore,the preparation of high-performance NiZn ferrite materials is one of the key factors in improving the performance of waveguide isolators.This paper first explores the impact of the Ni²⁺to Zn²⁺ratio on the properties of NiZn ferrite.Ni_xZn_1-xFe₂O₄（x=0.15,0.25,0.35,0.45,0.65,0.70,0.80 and 0.85）ceramic substrates were prepared by conventional sintering techniques.The microstructure and magnetic properties of NiZn ferrite ceramic substrates with different Ni²⁺contents were investigated.Then,Ni_0.65Zn_0.35Fe₂O₄ ceramic samples were prepared by hot-press sintering（HP）and spark plasma sintering（SPS）,and their properties were tested and analyzed.Due to the size limitations of the prepared NiZn ferrite ceramics,the NiZn ferrite ceramics prepared by conventional sintering were finally selected as the magnetized material to fabricate a waveguide isolator,and its electrical performance was tested.The study shows that:（1）Among the NiZn ferrite ceramic substrates with different Ni²⁺contents prepared by conventional sintering,Ni_0.65Zn_0.35Fe₂O₄ has the highest saturation magnetization of up to 78.68 emu/g,with a 4πM_S of 4780 Gs and a ferromagnetic resonance line width（ΔH）of 263 Oe.（2）The hot-press sintering temperature and holding time affect the magnetization properties of NiZn ferrite ceramic substrates.The sample prepared at a hot-press sintering temperature of 1010°C with a holding time of 20 minutes exhibits the best overall magnetic performance,with a saturation magnetization of 76.43 emu/g,4πM_S of 5041Gs,and a ferromagnetic resonance line width（ΔH）of 352 Oe.（3）The sintering temperature,pressure,and holding time in spark plasma sintering all influence the magnetization properties of NiZn ferrite ceramic substrates.The sample prepared at a sintering temperature of 1150°C,holding time of 5 minutes,and pressure of 1.5 t shows the best overall magnetic performance,with a saturation magnetization of up to 74.99 emu/g and 4πM_S of 4947 Gs.The waveguide isolator made from NiZn ferrite ceramics prepared by conventional sintering can stably operate within the working frequency range of 13.5 to 18.5 GHz.更多还原