SrFe12O19 based ceramics with ultra-low dielectric loss in the millimetre-wave band
Donnan, Robert S.
Reece, Michael J.
AffiliationQueen Mary University of London; Hunan University; National University of Defence Technology; University of Chester; Thomas Keating Ltd; Northwestern Polytechnical University
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AbstractNon-reciprocal devices such as isolators and circulators, based mainly on ferromagnetic materials, require extremely low dielectric loss in order for strict power-link budgets to be met for millimetre (mm)-wave and terahertz (THz) systems. The dielectric loss of commercial SrFe12O19 hexaferrite was significantly reduced to below 0.002 in the 75 - 170 GHz band by thermal annealing. While the overall concentration of Fe2+ and oxygen vacancy defects is relatively low in the solid, their concentration at the surface is significantly higher, allowing for a surface sensitive technique such as XPS to monitor the Fe3+/Fe2+ redox reaction. Oxidation of Fe2+ and a decrease in oxygen vacancies is found at the surface on annealing, which is reflected in the bulk sample by a small change in unit cell volume. The significant decrease in dielectric loss property can be attributed to the decreased concentration of charged defects such as Fe2+ and oxygen vacancies through annealing process, which demonstrated that thermal annealing could be effective in improving the dielectric performance of ferromagnetic materials for various applications.
CitationYu, C., Zeng, Y., Yang, B., Wylde, R., Donnan, R., Wu, J., ... & Yan, H. (2018). SrFe12O19 based ceramics with ultra-low dielectric loss in the millimetre-wave band. Applied Physics Letters, 112(14), 143501.
JournalApplied Physics Letters
DescriptionThe following article appeared in Applied Physics Letters, 112,143501 and may be found at https://doi.org/10.1063/1.5022271. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing.
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