The addition of a minor amount of Co2Y ferrites effects on the microstructure, magnetic properties and DC-bias superposition characteristics of NiCuZn ferrites were investigated in this study. It was observed that Co2Y can effectively act as the inert second phase to reduce grain mobility using the Zener pinning effect during sintering, and hence impede grain growth. The initial permeability of NiCuZn ferrites decreased, but the onset frequency for the increase in imaginary permeability as well as the resonance frequency both increased with increasing Co2Y addition due to the grain size effects. The figure of merit for NiCuZn ferrites for high frequency applications, (mu(i) - 1)f(r), and DC-bias-superposition characteristics can be effectively promoted by increasing Co2Y addition. A suitable compromise between the initial permeability and DC superposition characteristic can also be obtained by adding a proper amount of Co2Y to adjust the grain size. (C) 2014 Elsevier B.V. All rights reserved.