A series of polycrystalline Ba Zn2-x Mgx Fe16 O27 W-type hexagonal ferrite; (x = 0.0,0.4,0.8,1.2,1.6 and 2) were prepared by using the conventional ceramic method. The dielectric constant (ε′) and the dielectric loss tangent (tan δ ) were determined as functions of frequency, temperature and composition. The frequency dependence of the dielectric constant was found to exhibit two types of behaviour: the usual dispersion at low temperatures and an abnormal behaviour at relatively high temperatures which could be explained on the basis of Rezlescu and Rezlescu assumption, which attributes this abnormal behaviour to a collective contribution of two types of charge carriers to the polarization.
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