Dielectric properties of rare earth substituted Cu-Zn ferrites

Samples with the chemical formula Cu0.5Zn0.5Fe2-xRxO4 (R = La, Nd, Sm and Gd; x = 0 and 0.1) were prepared by the standard ceramic method. The real part of the dielectric constant epsilon' and the ac electrical conductivity sigma(ac) are measured and the dielectric loss tangent tan delta is calculated in the frequency range 50-10(5) Hz and from room temperature up to congruent to 800 K. epsilon' and tan delta are found to decrease with increasing the frequency while sigma(ac) is generally increased. On the contrary epsilon', sigma(ac) and tan delta are increased with temperature. No relaxation was detected in tan delta(f) in the investigated frequency range while tan delta(T) showed two maxima. The composition dependence of the dielectric parameters is discussed and the results are explained using Koops's model. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.