Complex permittivity and permeability dependence of Ba4Zn2-ZCoZFe36O60U-type hexaferrites prepared by citrate sol-gel on composition, annealing temperature and frequency

The present paper deals with the investigations of the preparation of hexaferrites with Z = 0.0, 0.5, 1.0, 1.5, 2.0 by citrate sol-gel process as well as the complex dielectric constant and complex permeability as functions of measuring frequency from 100 MHz to 6 GHz, annealing temperature and composition. The results show that the real part of permeability decreased with frequency increasing for all samples annealed at 1000-1200 degreesC but Co2U ferrite (Ba4Co2Fe36O60). The natural resonance phenomenon is observed in u" spectrum for all hexaferrites with exception for Co2U. The natural resonance frequency is a function of annealing temperature as well as composition, which shifts to lower frequency with Zinc content and increasing calcaining temperature. (C) 2002 Elsevier Science B.V. All rights reserved.