Effects of NiO addition on the structural, microstructural and electromagnetic properties of manganese–zinc ferrite

Abstract

Structural, microstructural and electromagnetic properties of NiO doped manganese–zinc (MnZn) ferrites prepared by a solid-state reaction method have been investigated. The continuous doping of NiO resulted in an increase in lattice constant ( a), porosity ( P) and electrical resistivity ( ρ), a decrease in average grain size ( D) and bulk density ( d b), while no obvious change in X-ray density ( d X). Hysteresis loss ( P h) increased monotonically with increasing NiO, and its variation could be explained by the relation: P h ∝ 1 / μ i 3 , where μ i was initial permeability. Eddy current loss ( P e) first reduced before achieving its minimum, and then rose gradually. The variation of P e was inconsistent with the classical expression, P e,cl ∝ D 2/ ρ, where D and ρ were average grain size and resistivity, respectively, and the excess loss ( P e,exc) could contribute to the P e. Residual loss ( P r) reduced slowly due to D’s decrease and f r’s increase which were caused by the increase in NiO, where f r was resonance frequency. Finally, the sample doped with 0.10 wt% NiO showed the lowest losses of 207 kW m −3 at 100 °C, 1 MHz and 30 mT.