Synthesis of single crystal and microwave characteristics of magnetoplumbite type Ferrite

千兆赫波段的微波辐射越来越多地应用于各种通信设备中。在六角形m型铁氧体或w型铁氧体中，在48 GHz频率附近会出现磁共振现象。研究表明，用Ti、Mn等金属取代BaFe_12O_19中的Fe^<3+>，使共振频率从50 GHz左右降低到10 GHz以下。然后发现该铁氧体可以用作微波吸收剂或对抗EMI（电磁兼容）。为了改善六方铁氧体的吸收特性，合成了具有物质固有性质的单晶铁氧体。用布里格曼法在两段式电炉中进行了晶体生长。将Fe_2O_3与BaCO_3的混合物按化学配方abafe_12o_19的比例制成球团，在1300℃下煅烧，粉碎至几μm大小，制备成晶体生长。将粉末放入Pt坩埚中，加热至1450℃以上。熔体保持在1450℃，冷却速度为2-10mm/h（冷却速度为5-10℃/h）至1250℃。当整个熔体凝固后，坩埚落入水中淬火。铸锭表面呈蜂窝状晶界分布。每个六角形面都有金属光泽。这些都是由钻石切割切割和分析x射线劳埃照片。每一块都是单晶，表明六边形对称。这些样品在六方铁氧体中平行于c轴或c面切割，并用vsm制备磁性测量。饱和磁化强度Ms为80emu /g，矫顽力iHc为4kOe。用网络分析仪测量了样品在1 ~ 20 GHz范围内的微波特性（复磁导率μ和介电常数ε）。Ba铁氧体在48GHz附近出现磁共振。因此需要将谐振频率控制在1-20 GHz的频率范围内，用于实际应用。然后用Ti、Mn、Sn、Zr等金属代替Ba铁氧体中的Fe^<3+>，研究对微波特性的影响。目前正在尝试和合成金属取代钡铁氧体单晶。少

Microwave radiation in the GHz band is increasingly being used in many various communication devices. Magnetic resonance phenomenon is known to appear near the frequency of 48 GHz in hexagonal M-type ferrite or W-type ferrite. It has been studied that the substitution by metal such as Ti, Mn and so on for Fe^<3+> in BaFe_12O_19 caused the reduction of resonance frequency from about 50 GHz to less than 10 GHz. And then this ferrite was found to be used as microwave absorber or countermeasure to EMI(elecromagnetic compatibility). Furthrermore, single crystal ferrite which show the inheret properties of substance, has been synthesized in order to improve the absorber characteristics of hexagonal ferrite. Crystal growth has been carried out in two stage electric furnace by Bridgmann method. The mixture of Fe_2O_3 and BaCO_3 powders in according to the ratio of chemical formulaBaFe_12O_19 were pelletized and calcinated at 1300℃, and crushed to the size of a few μm and prepared for crystal g … More rowth. Powder was put into Pt crucible and heated to more than1450℃(m.p.). The melt was hold at 1450℃ and lowered down at 2-10mm/h (cooling rate :5-10 ℃/h) to 1250℃. After the whole melt soidified, the crucble was fall down into water and quenched. The surface of ingot was portioned with grain boundarys, like as honeycomb structure. Each hexagonal facet has metalic luster. These were cut off by a diamond cutter and analized by X-ray Laue photuograph. Each pieces were single crystals indicating hexagonal symmetry. These samples were cut pararelly to c-axis or c-face in hexagonal ferrite, and prepared for magnetic measurement by vsm. The saturation magnetization Ms and the coercive force iHc are 80 emu/g and 4kOe, respectively. Also these samples were formed to toroidal shape and measured microwave characteristics (complex permeability μ and permittivity ε) in the range of 1-20 GHz by a network analyzer. The magnetic resonance appear near 48GHz in Ba ferrite. Therefore the resonance frequency need to be controlled to the frequency range of 1-20 GHz, which are used for practical application. And then, the substitution of metal such as Ti, Mn, Sn and Zr for Fe^<3+> in Ba ferrite was carried out, to investigate the effects on the microwave characteristics. At present, sigle crystal of metal substituted Ba ferrite is being tried and synthesized. Less