Dataset Information

Thermal frequency shift and tunable microwave absorption in BiFeO3 family.

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.

SUBMITTER: Li Y

PROVIDER: S-EPMC4837409 | biostudies-literature | 2016 Apr

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Thermal frequency shift and tunable microwave absorption in BiFeO3 family.

Li Yong Y Fang Xiaoyong X Cao Maosheng M

Scientific reports 20160420

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 te ...[more]

PMID: 27093897

Similar Datasets

Project description:This work presents lightweight epoxy foams loaded with very low weight percentages (≤0.5 wt.%) of carbon fibers (CFs) with different lengths (3 mm, 6 mm, and 12 mm) as broadband microwave absorbing materials for anechoic chamber application. The effect of CF length on microwave absorption, especially on the absorption frequency band, is investigated for frequencies between 1 and 15 GHz. For the elaboration of composites, three different methods-spatula, shear mixing, and ultrasounds-are used for the dispersion of CFs. The observation of these CFs, after the dispersion step, shows a high fiber breakage rate when shear mixing is used, unlike when spatula or ultrasounds methods are used. On the other hand, the characterization of the elaborated composites highlights a correlation between the mixing methods, hence the fiber brakeage, and the measured reflection coefficient (reflection loss) of the composites. As a result, the minimum value of the reflection coefficient is shifted toward the high frequencies when the fiber breakage is observed, suggesting that short CFs absorb at high frequencies while long CFs absorb at low frequencies. Dielectric properties, extracted from the measurement in free space, of composites elaborated with different fiber lengths (3 mm, 6 mm, and 12 mm) confirm that short CFs (3 mm) show maximum losses at high frequencies (around 15 GHz) while long CFs (12 mm) show maximum dielectric losses at low frequencies (below 4 GHz). However, no significant variation is observed on the real part of the relative permittivity, as a function of fiber length, for these porous composites loaded with very low CF rates. A hybrid composite, with a mix of different CF lengths, is prepared and characterized. The simulation of the absorption performance of a pyramidal absorber, based on this hybrid composite, is compared to the one of pyramidal absorber based on composites loaded with a single length of carbon fibers. The pyramidal absorber-based hybrid composite predicts the best absorption performance, especially at the low frequency band. The simulated reflection coefficient of this absorber is less than -12 dB in all the studied frequency range, and less than -40 dB for frequencies higher than 3 GHz. This result confirms the interest of using a mix of carbon fiber lengths to achieve a broadband microwave absorber.

Dataset Information

Thermal frequency shift and tunable microwave absorption in BiFeO3 family.

Publications

Thermal frequency shift and tunable microwave absorption in BiFeO3 family.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets