Dielectric behavior of Mn-substituted Co2Z hexaferrites

In order to improve the properties of multi-layer chip inductor device, the dielectric constant and loss tangent as functions of frequency, temperature and composition for a series of samples of Ba3Co2Fe23-12xMn12xO41 hexagonal ferrites were studied. For all samples, a single Z-type phase was established and the lattice constants were calculated. Results show that dielectric constant increases as sintering temperature increases, dielectric constant and loss tangent decrease as frequency increases and as temperature decreases. These effects are attributed to the Maxwell-Wagner double-layer polarization. As the Mn-substitution increased, samples showed abnormal dielectric behavior in the form of relaxation peaks which shifted toward higher frequencies, dielectric constant epsilon' and loss tangent also decrease gradually reaching minimum between x = 0.02 and 0.06. The polarization can be explained by the hopping mechanism in that Mn substitution for Fe ions on the B-sites acts to reduce Fe2+ formation. A second mechanism that small polarons may also contribute to the polarization is indicated in this work. (C) 2002 Elsevier Science B.V. All rights reserved.