| Abstract |
| Perovskite manganese La0.7Sr0.3MnO3 (LSMO) powders were prepared by sol-gel synthesis and calcination in the temperature (T) range of 500~1200 ℃ and their structures and electromagnetic (EM) wave absorption properties were investigated. X-ray diffraction (XRD) analysis revealed that the crystalline perovskite phase can be formed at T ≥ 600 ℃. The average grain size was ~15 nm at the calcination temperature (Tcal) = 600 ℃ and it increased to ~1 μm when Tcal increased up to 1200 ℃. MH curves of the samples showed soft magnetic behaviors for all the crystallized samples, and the value of saturation magnetization increased with increasing Tcal. The real and imaginary parts of permittivities and permeabilities were measured on LSMO powder-epoxy (10 wt%) composites using a network vector analyzer in the frequency range of 100 MHz ≤ f ≤ 18GHz. The complex permittivities (ε', ε") increased significantly in samples calcined above 800 ℃ because the concentration of free electrons increased, due to the LSMO's unique magnetotransport effect, as the crystallinity and the MS value increased significantly. As the Tcal increased, the height of the μ' and μ" spectra also gradually increased. The large values of ε', ε" of the LSMO-epoxy are dominant factors in the EM wave absorption characteristics, and it showed good absorption characteristics when it had a thickness of 1.5 mm or less at a frequency of 12 GHz or higher. At the same time, it also exhibited EM wave shielding ability by reflection in the several GHz band.
(Received 12 October, 2022; Accepted 28 November, 2022) |
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| Key Words |
| LSMO, sol-gel method, permittivity, permeability, reflection loss, EM absorption |
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