High-resistivity nickel-zinc ferrites by the citrate precursor method

Nickel-zinc ferrites of different compositions, Ni1-xZnxFe2O4 with x = 0.2, 0.35, 0.5 and 0.6, have been prepared by a precursor method involving citr ate precursors of the concerned metals and mixing them in solution state. R esistivity has been studied as a function of composition and sintering temp erature. It is observed that NiZn ferrites prepared by this method have res istivity greater than or equal to 10(8) Omega cm which is higher by at leas t two orders of magnitude than that reported (less than or equal to 10(6) O mega cm) for ferrites prepared by the conventional ceramic method. This is attributed to better purity as well as better compositional and microstruct ural control achievable by the citrate method. High resistivity makes these ferrites suitable particularly for high-frequency applications where eddy current losses are required to be low. (C) 1999 Elsevier Science B.V. All r ights reserved.