Electrical and magnetic properties of magnesium ferrite ceramics doped with Bi2O3
Electrical and magnetic properties of magnesium ferrite ceramics doped with Bi2O3
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DOI：
10.1016/j.actamat.2007.08.011
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发表时间：
2007-11
期刊：
影响因子：
9.4
通讯作者：
L. Kong;Zhaoliang Li;G. Lin;Y. Gan
中科院分区：
文献类型：
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作者：
L. Kong;Zhaoliang Li;G. Lin;Y. Gan
研究了Bi 2 O3含量和烧结温度对MgFe 1.98O4铁氧体陶瓷直流电阻率、复相对介电常数和磁导率的影响。该研究的目的是开发磁介电材料，其磁导率和介电常数几乎相等，以及低磁和介电损耗角正切，用于设计物理尺寸减小的天线。结果表明，Bi 2 O3的加入可以改善MgFe 1.98O4烧结体的致密性差和晶粒生长速度慢的缺点，这是由于Bi 2 O3的低熔点有利于液相烧结。结果表明，添加3%Bi_2O_3可使MgFe_（1.98）O_4陶瓷完全烧结。除0.5%外，Bi 2 O3的加入均使MgFe 1.98O4陶瓷的直流电阻率增加。0.5%样品的异常低的结晶度是由样品晶界处的少量液相的“清洁”效应解释的。MgFe1.98O4陶瓷的电磁性能与Bi 2 O3的浓度有很强的依赖性。发现0.5%样品具有最高的介电损耗角正切，这可以类似于DC电阻率结果来理解。为获得低介电损耗的MgFe 1.98O4天线陶瓷，需要添加2-3%的Bi 2 O3。低浓度的Bi 2 O3提高了MgFe 1.98O4陶瓷的静态磁导率，由于提高致密化和晶粒生长，而过高的浓度导致磁导率下降，由于纳入非磁性组分（Bi 2 O3）和延迟晶粒生长。然而，单独添加Bi 2 O3不能产生基于MgFe1.98O4陶瓷的磁介电材料，并且需要进一步的工作来使用钴（Co）来修改磁导率。
The effects of concentration of Bi2O3and sintering temperature on DC resistivity, complex relative permittivity and permeability of MgFe1.98O4ferrite ceramics were studied. The objective of the study was to develop magneto-dielectric materials, with almost equal values of permeability and permittivity, as well as low magnetic and dielectric loss tangent, for the design of antennas with reduced physical dimensions. It was found that the poor densification and slow grain growth rate of MgFe1.98O4can be greatly improved by the addition of Bi2O3, because liquid phase sintering was facilitated by the formation of a liquid phase layer due to the low melting point of Bi2O3. It was found that 3% Bi2O3can result in fully sintered MgFe1.98O4ceramics. The DC resistivities of the MgFe1.98O4ceramics were increased as a result of the addition of Bi2O3, except for 0.5%. The exceptionally low resistivities of the 0.5% samples were explained by a ‘cleaning’ effect of the small amount of liquid phase at the samples’ grain boundaries. The electrical and magnetic properties of the MgFe1.98O4ceramics exhibited a strong dependence on the concentration of Bi2O3. The 0.5% samples were found to have the highest dielectric loss tangents, which can be understood similarly to the DC resistivity results. The 2–3% Bi2O3is required to attain low dielectric loss MgFe1.98O4ceramics for antenna application. Low concentration of Bi2O3increased the static permeability of the MgFe1.98O4ceramics owing to the improved densification and grain growth, while too high a concentration led to decreased permeability owing to the incorporation of the non-magnetic component (Bi2O3) and retarded grain growth. However, the addition of Bi2O3alone is not able to produce magneto-dielectric materials based on MgFe1.98O4ceramics, and further work is necessary to modify the permeability using cobalt (Co).