Thermal frequency shift and tunable microwave absorption in BiFeO3 family.
Thermal frequency shift and tunable microwave absorption in BiFeO3 family.
复制标题
BiFeO3 系列的热频移和可调谐微波吸收
DOI：
10.1038/srep24837
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发表时间：
2016-04-20
影响因子：
4.6
通讯作者：
Cao M
中科院分区：
文献类型：
--
作者：
Li Y;Fang X;Cao M
可调谐频率因其在频率选择、吸波材料、成像和生物医学诊断等方面的应用潜力而备受研究者们的追捧。本文报道了在300-673K温度范围内首次观测到的La/Nd掺杂BiFeO_3(BFO)在X波段的介电弛豫热频移。弛豫最大位移约为X波段的四分之一。晶格振动的非线性项在频移中起着重要作用。频移导致了微波吸收的调谐，通过改变温度几乎覆盖了整个X波段。同时，由于热激发电子跃迁导致La/Nd掺杂BFO的介电损耗显著增加，使BFO的微波吸收分别提高到~460K和~480K以上。在673K时，掺La/Nd的BFO的微波吸收大于−20dB，最小反射损耗达到−39dB。这些结果为发展BFO基电磁功能材料和器件开辟了一条新的途径，可用于频率可调、隐身和长波长热成像。
Tunable frequency is highly sought-after task of researcher, because of the potential for applications in selecting frequency, absorber, imaging and biomedical diagnosis. Here, we report the original observation of thermal frequency shift of dielectric relaxation in La/Nd doped BiFeO3 (BFO) in X-band from 300 to 673 K. It exhibits an unexpected result: the relaxation shifts to lower frequency with increasing temperature. The relaxation maximally shifts about a quarter of X-band. The nonlinear term of lattice vibration plays an important role in the frequency shift. The frequency shift leads to tuning microwave absorption, which almost covers the whole X-band by changing temperature. Meanwhile, the great increase of dielectric loss of La/Nd doped BFO due to thermal excited electron hopping enhances microwave absorption above ~460 and ~480 K, respectively. The microwave absorption of La/Nd doped BFO surpasses −20 dB at 673 K and the minimum reflection loss of La doped BFO reaches −39 dB. These results open a new pathway to develop BFO-based materials in electromagnetic functional materials and devices for tunable frequency, stealth and thermal imaging at long wavelength.