Title :
Low Loss Z-Type
Hexaferrites for Antennas and RF Devices
Author :
Zhang, Lanlin ; Puri, Archana ; Sertel, Kubilay ; Volakis, John L. ; Verweij, Henk
Author_Institution :
Mater. Sci. & Eng. Dept., Ohio State Univ., Columbus, OH, USA
Abstract :
Z-type hexaferrites are considered for applications in the 10 MHz to 1 GHz band due to their potential to overcome Snoek´s limit. However, state-of-art hexaferrites have high magnetic loss, related to substantial micro-structural inhomogeneity and processing details. The dependence of magnetic properties on the ceramic processing route is demonstrated in this paper for Ba3Co2Fe24O41 (Co2Z) compositions. Fine Co2Z powders prepared by wet-chemical synthesis were used to obtain different microstructures through dry or colloidal compaction, followed by sintering with different temperature programs. Large variations in permeability and loss behavior were found between samples with different processing histories and hence microstructures. The best results obtained were μr´ ~ 2.5 and μr´´ <; 0.2 (tanδ ≤ 0.1) for the 10 to 930 MHz band. This is a significant improvement w.r.t. previously reported values.
Keywords :
Snoek effect; barium compounds; cobalt compounds; crystal microstructure; eddy current losses; ferrites; magnetic leakage; magnetic permeability; microwave antennas; powders; sintering; Ba3Co2Fe24O41; RF device; Snoek limit; antennas; ceramic processing route; colloidal compaction; frequency 10 MHz to 1 GHz; low loss Z-type hexaferrites; magnetic loss; microstructural inhomogeneity; permeability; powders; sintering; state-of-art hexaferrites; wet-chemical synthesis; Ferrites; Magnetic properties; Magnetic resonance imaging; Microstructure; Permeability; Powders; Resonant frequency; ${rm Ba}_{3}{rm Co}_{2}{rm Fe}_{24}{rm O}_{41}$ hexaferrite; ${rm Co}_{2}{rm Z}$; magnetic permeability;
Journal_Title :
Magnetics, IEEE Transactions on
DOI :
10.1109/TMAG.2011.2128876