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Thermal frequency shift and tunable microwave absorption in BiFeO3 family.

Li Y, Fang X, Cao M - Sci Rep (2016)

Bottom Line: It exhibits an unexpected result: the relaxation shifts to lower frequency with increasing temperature.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.

View Article: PubMed Central - PubMed

Affiliation: School of Material Science and Engineering, Beijing Institute of Technology, Beijing 100081, China.

ABSTRACT
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.

No MeSH data available.


The complex permittivity of (a) BFO, (b) La doped BFO and (c) Nd doped BFO in X-band from 300 to 673 K.
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f1: The complex permittivity of (a) BFO, (b) La doped BFO and (c) Nd doped BFO in X-band from 300 to 673 K.

Mentions: The dielectric properties were measured in microwave frequency range (X-band, 8.2–12.4 GHz) from 300 to 673 K by the high-temperature waveguide test apparatus. The real and imaginary permittivity versus frequency at elevated temperature is shown in Fig. 1. The real permittivity of BFO and La/Nd doped BFO in this study decreases with increasing frequency, and increases with increasing temperature, demonstrating dispersion response over the full X-band and strong temperature dependence. The relaxation peaks are found in imaginary permittivity of all samples, which exhibit dielectric relaxation behavior. The imaginary permittivity increases with increasing temperature for all samples. BFO exhibits a slow growth over the investigated temperature, while La/Nd doped BFO have an abrupt rise at ~460 and ~480 K, respectively (Fig. S1).


Thermal frequency shift and tunable microwave absorption in BiFeO3 family.

Li Y, Fang X, Cao M - Sci Rep (2016)

The complex permittivity of (a) BFO, (b) La doped BFO and (c) Nd doped BFO in X-band from 300 to 673 K.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4837409&req=5

f1: The complex permittivity of (a) BFO, (b) La doped BFO and (c) Nd doped BFO in X-band from 300 to 673 K.
Mentions: The dielectric properties were measured in microwave frequency range (X-band, 8.2–12.4 GHz) from 300 to 673 K by the high-temperature waveguide test apparatus. The real and imaginary permittivity versus frequency at elevated temperature is shown in Fig. 1. The real permittivity of BFO and La/Nd doped BFO in this study decreases with increasing frequency, and increases with increasing temperature, demonstrating dispersion response over the full X-band and strong temperature dependence. The relaxation peaks are found in imaginary permittivity of all samples, which exhibit dielectric relaxation behavior. The imaginary permittivity increases with increasing temperature for all samples. BFO exhibits a slow growth over the investigated temperature, while La/Nd doped BFO have an abrupt rise at ~460 and ~480 K, respectively (Fig. S1).

Bottom Line: It exhibits an unexpected result: the relaxation shifts to lower frequency with increasing temperature.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.

View Article: PubMed Central - PubMed

Affiliation: School of Material Science and Engineering, Beijing Institute of Technology, Beijing 100081, China.

ABSTRACT
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.

No MeSH data available.