Doping effect on complex permeability and permittivity for W -type barium ferrite composites

Abstract

Doping effects on crystal structure, static, and dynamic magnetic properties have been investigated for BaCoZnFe16 O27 doped with 0.5 wt % CaO, Bi2 O3, SiO2, 0.5 and 1.0 wt % Nb2 O5 and V2 O5, as well as their ferrite/epoxy composites. The results show that the doping can greatly modify the high-frequency dynamic properties of the composites. As compared to the undoped composite, doping of CaO, Bi2 O3, and SiO2 significantly increases complex permittivities ′ and ″. The increase has its origin in the formation of Fe2+ ions caused by the doping. Doping of CaO, Bi2 O3, Nb2 O5, and V2 O5 leads to a considerable increase in static permeability μ0′. Further, the doping of V2 O5 can significantly increase the maximum imaginary permeability μ max ″. Based on the curve-fitted results to complex permeability spectra, the former is attributed to the enhanced wall permeability and the latter is related to the decrease in effective damping coefficient. However, the resonance is shifted to lower frequency for all composites doped with various oxides. © 2007 American Institute of Physics.