Development of magneto-dielectric materials based on Li-ferrite ceramics I. Densification behavior and microstructure development
Development of magneto-dielectric materials based on Li-ferrite ceramics I. Densification behavior and microstructure development
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DOI：
10.1016/j.jallcom.2007.05.050
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发表时间：
2008-07
影响因子：
6.2
通讯作者：
M. Teo;L. Kong;Zhaoliang Li;G. Lin;Y. Gan
中科院分区：
文献类型：
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作者：
M. Teo;L. Kong;Zhaoliang Li;G. Lin;Y. Gan
锂铁氧体陶瓷的直流电阻率和介电性能掺杂Bi 2 O3（0-5wt%）并用Co改性的（Li0.50Fe2.50O4）（Li0.50 - 0.50xCoxFe2.50 - 0.50xO4，其中x=0.01-0.07），主要目的是开发具有匹配的磁导率和介电常数以及低的磁损耗和介电损耗角正切的磁介电材料，用于HF天线的小型化。由于Li0.50Fe2.50O4陶瓷不能在≤1100°C的温度下烧结，高温烧结会导致Fe 2+离子的形成，因此不可能获得低介电损耗的纯Li0.50Fe2.50O4陶瓷。虽然1%的Bi 2 O3足以在850-1100°C下获得完全致密的Li0.50Fe2.50O4陶瓷，但它不足以生产介电损耗角正切≤10−2的材料。需要高浓度（3%）的Bi 2 O3，结合≤950°C的烧结温度，以在感兴趣的频率范围（3- 30 MHz或HF波段）内获得≤10− 2的足够低的介电损耗角正切。Li0.50Fe2.50O4陶瓷的相对介电常数和介电损耗角正切的变化作为Bi 2 O3的浓度和烧结温度的函数，可以理解的微观结构的发展。Co对Li_（0.50）Fe_（2.50）O_4陶瓷介电性能的影响远小于Bi_2 O_3。
DC resistivity and dielectric properties of the Li-ferrite ceramics (Li0.50Fe2.50O4) doped with Bi2O3(0–5wt%) and modified with Co (Li0.50−0.50xCoxFe2.50−0.50xO4, with x=0.01–0.07) were investigated, with a primary objective to develop magneto-dielectric materials with matching permeability and permittivity and low magnetic and dielectric loss tangent, for miniaturization of HF antennas. It is impossible to obtain pure Li0.50Fe2.50O4ceramics with low dielectric loss tangent because it cannot be sintered at temperature of ≤1100°C and high temperature sintering will lead the formation Fe2+ions. Although 1% Bi2O3is sufficient to obtain fully dense Li0.50Fe2.50O4ceramics over 850–1100°C, it is insufficient to produce materials with a dielectric loss tangent of ≤10−2. A high concentration (3%) Bi2O3, combined with sintering temperature of ≤950°C, is required to attain sufficiently low dielectric loss tangent of ≤10−2over the frequency range of interest (3–30MHz or HF band). The variation of relative permittivity and dielectric loss tangent of the Li0.50Fe2.50O4ceramics as a function of the concentration of Bi2O3and sintering temperature can be understood in terms of the microstructure developed. It is also found that the effect of Co on the dielectric properties of Li0.50Fe2.50O4ceramics is much less than that of Bi2O3.