Fe THIN FILMS GROWN ON SURFACE OF SrFe12O19 BY MOCVD METHOD AND ITS ABSORBING PROPERTIES
LIU Yuan, LIU Xiangxuan, WANG Xuanjun, CHEN Xin
No.603 Faculty, Xi'an Research Institute of High Technology, Xi'an 710025
Cite this article:
LIU Yuan, LIU Xiangxuan, WANG Xuanjun, CHEN Xin. Fe THIN FILMS GROWN ON SURFACE OF SrFe12O19 BY MOCVD METHOD AND ITS ABSORBING PROPERTIES. Acta Metall Sin, 2014, 50(9): 1095-1101.
Nowadays, more and more researchers pay attention to the microwave absorbing materials with the increase of electromagnetic pollution and the development of stealth technology for military platforms. Traditional microwave absorbers, such as ferrite, metal powder, conductive magnetic fibers, magnetic flake powder, and nanoparticles and so on, are facing some common problems such as large specific gravity, narrow absorption bandwidth, large match thickness and poor absorption performance. Composites with core-shell structures are becoming promising microwave absorbing material because such structure can exhibit magnetic and dielectric characteristics through the proper selection of core and shell materials. Thus, Fe(CO)5 deposition on the SrFe12O19 surface has been considered for the fabrication of a new composite that possesses the advantages of these two materials. This new composite might also obtain remarkable microwave absorption through thin layer absorbers in the entire 2~18 GHz frequency range. The Fe-SrFe12O19 composites with core-shell structures were prepared by metal organic chemical vapor deposition (MOCVD) using the SrFe12O19 and iron pentacarbonyl [Fe(CO)5] as the precursors. XRD, SEM, EDS and a vector network analyzer were used to characterize the structure and electromagnetic properties of the samples. The structure and morphology analyses show that the composites have complete core-shell structures with SrFe12O19 as core and Fe layers as shell. Fe nanoparticles were uniformly deposited on the surface of SrFe12O19 with thickness of about 0.5 mm at the reaction temperature of 180 ℃ with N2 flow rate of 30 mL/min for 30 min. Simulation studies show that SrFe12O19 electromagnetic properties changed significantly and the absorbing properties got evidently improvement after Fe deposited on its surface. The samples prepared with deposition time of 30 min have the best absorbing properties. A reflection loss (RL) value exceeding -10 dB in the range of 6.8~18.0 GHz frequency was obtained by selecting an appropriate thickness of the absorber layer from 1.5 to 3.0 mm. Moreover, a minimum RL of -21.2 dB at was obtained for a 2.0 mm thick layer. Fe-deposited SrFe12O19 by MOCVD can significantly improve the electromagnetic properties of SrFe12O19 and Fe-SrFe12O19 composites could be used as an effective microwave absorption material.
Fig.1 XRD spectra of Fe-SrFe12O19 after different reaction times
Fig.2 SEM images of SrFe12O19 (a) and Fe-SrFe12O19 after reaction times of 10 min (b), 30 min (c) and 60 min (d)
Fig.3 SEM image of Fe-SrFe12O19 (a) and the EDS analysis (b)
Fig.4 Real (a, c) and imaginary (b, d) parts of the complex permittivity (a, b) and permeability (c, d) of SrFe12O19 and Fe-SrFe12O19 (e′—real part of permittivity, e′′—imaginary part of permittivity, m′—real part of permeability, m′′—imaginary part of permeability)
Fig.5 Values of f- -1(m')-2m'' versus frequency of Fe-SrFe12O19 (f—frequency)
Fig.7 Three-dimensional microwave absorbing renderings of SrFe12O19 (a) and Fe-SrFe12O19 (b)
Fig.8 Reflection loss of Fe-SrFe12O19 with thickness of 1.5~3.0 mm (a) and comparison of measured and calculated reflection loss for Fe-SrFe12O19 (b)
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