J. Phys. IV France 07 (1997) C1-423-C1-424
The Effect of Nonstoichiometry on Microwave Absorbing Properties of Ni-Zn FerritesS.-S. Kim1 and I.G. Choi2
1 Department of Materials Engineering, Chungbuk National University, Cheongju 360-763, Korea
2 Department of Radio Engineering, Chungbuk National University, Cheongju 360-763, Korea
Microwave absorbing properties of the nonstoichiometric compounds of Ni-Zn ferrites with excess Fe2O3 are investigated. Toroidal compacts of (Ni0.5Zn0.5O)1-y(Fe2O3)1+y spinels are prepared by the conventional ceramic processing technique. The magnetic permeability and dielectric constant are greatly dependent upon the amount of excess Fe2O3 (y>0). Both the real and imaginary components of permeability decrease as the excess Fe2O3 increases. On the other hand, the dielectric constant increases with the increase of excess Fe2O3. The combined effect of high dielectric constant and low permeability results in a lower-frequency impedance matching. The plate thickness at the zero-reflection frequency is predicted using the approximated impedance-matching relationship between wavelength and material parameters.
© EDP Sciences 1997