Processing of nickel-zinc ferrites via the citrate precursor route for high-frequency applications

Nickel-zinc ferrites of various compositions, Ni1-xZnxFe2O4 where x = 0.2, 0.4, 0.5, and 0.6 investigated in the present work, have been prepared by the citrate precursor method. The complex Permittivity (epsilon'-j epsilon) and permeability (mu'-mu) of the ferrites were measured at X-band (8-12 GHz) microwave frequencies. The dielectric constants or the real part of permittivity, E, are observed to lie in the range 5.46-8.95 for ferrites sintered at 1200 degrees C, while those sintered at 1300 degrees C exhibit relatively higher dielectric constants. The permittivity loss, tan 8, ( = epsilon/epsilon'), is observed to be of the order of 10(-2)-10(-3), depending upon the composition and sintering temperature of the ferrite. These losses are lower by at least one to two orders of magnitude compared with those normally reported for ferrites processed by the conventional ceramic method. The presently studied ferrites also exhibit high values of DC-resistivity, 10(7)-10(11) Omega (.) cm. The low dielectric losses and high resistivity can be co related to small grain size and better compositional stoichiometry obtained as a result of processing via the citrate route. Magnetic properties such as the Curie temperature, saturation magnetization, initial permeability, and B-H hysteresis parameters of the compositions with x = 0.5 and 0.6 are also given.