Influence of B 2 O 3 on the Broadband Electromagnetic Response of MgFe 1.98 O 4 Ceramics
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https://doi.org/10.1007/s11664-020-08482-3 2020 The Minerals, Metals & Materials Society
Influence of B2O3 on the Broadband Electromagnetic Response of MgFe1.98O4 Ceramics V. ADERSH1 and G. SUBODH
1,2
1.—Department of Physics, University of Kerala, Thiruvananthapuram, Kerala 695581, India. 2.—e-mail: [email protected]
MgFe1.98O4 ceramic has been synthesized by a solid-state reaction route, and the effect of different concentrations of B2O3 (0.5 wt.%, 1 wt.%, 2 wt.%, and 5 wt.%) on its broadband electromagnetic response is investigated. B2O3 acts as a liquid-phase sintering aid that reduces the sintering temperature of MgFe1.98O4 to 1100C without changing the bulk density. X-ray diffraction analysis confirms that MgFe1.98O4 ceramic is phase pure even after the addition of B2O3. The vibrational modes are identified using Raman and Fourier transform infrared (FTIR) spectroscopic analysis. The disorder effect and the associated splitting that occurred in the Raman modes confirm the inverse spinal structure of B2O3-modified MgFe1.98O4 ceramics. The compositions with 1 wt.% and 2 wt.% of B2O3 have real permittivity of 8.9 and 9.8, real permeability of 4.7 and 6.2, respectively, and reasonably low dielectric loss of the order of 101 at 100 MHz. Further, 1 wt.% and 2 wt.% B2O3 added compounds show room-temperature saturation magnetization of 26.1 and 25.6 emu/g and coercive field strength of 20 and 23 Oe, respectively. The broadband electromagnetic response shows that MgFe1.98O4 with 1 wt.% and 2 wt.% B2O3 can be used as a suitable substrate material for antenna fabrication. Key words: Magnesium ferrite, densification, sintering, permittivity, permeability, grain size
INTRODUCTION There is high demand for thinner, lighter, and multifunctional electronic devices in industrial, military, and medical fields. To achieve these goals, the physical dimensions of the antenna should be reduced without significant degradation of its performance. In a conventional dielectric antenna, to reduce the dimensions, high-permittivity antenna material has been used. However, this approach has drawbacks such as field confinement in the highpermittivity region and impedance mismatch. The best solution to this problem is to use magnetodielectric materials for antenna fabrication. In such
(Received June 11, 2020; accepted September 10, 2020)
magneto-dielectric wavelength is
antennas, C k ¼ pffiffiffiffiffiffiffiffi ; f lr er
the
transmission
ð1Þ
where f is the resonant frequency, lr is the relative permeability, er is the relative permittivity, and c is the velocity of light in free space.1 The increase in permeability can shorten the transmission wavelength and hence reduce antenna size without the problem of field confinement. Further, by choosing materials with matching permittivity and permeability, the impedance mismatch can be avoided.2 The development of novel magneto-dielectric materials and tuning of their properties for antenna miniaturization are current research trends. Ferrites are a class of magneto-dielectric materials that are wi
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