Effects of NiO addition on the microstructure, elemental distribution and magnetic properties of Mn-Zn power ferrites

Microstructure, elemental distribution and magnetic properties of NiO-doped Mn-Zn ferrites prepared by a conventional oxide ceramic process have been investigated. With the increase of NiO addition the grain size of Mn-Zn ferrites decreases and the temperature at which the maximum initial permeability as well as the lowest power loss appears increases. When the NiO concentration is 0.1 wt%, the density (d), saturation magnetization (Ms), initial permeability (μi), electrical resistivity (ρ) and power loss (PL) are improved, which can be attributed to the low porosity and fine microstructure. However, the density decreases and magnetic properties deteriorate with the appearance of irregular particles and crevice zones when the NiO concentration exceeds 0.1 wt%. We believe that the NiO acts as the nucleus of the irregular particles, which hinder the domain wall action and thus deteriorate the magnetic properties. The optimal values of d (4.91 g/cm3), Ms (4.26 × 105 A/m at 25 °C), μi (2312 at 25 °C), ρ (8.14 Ω m at 25 °C) and PL (369 kW/m3 at 100 °C, 100 kHz, 200 mT) are obtained for the ferrites with 0.1 wt% NiO, which are very promising for applications.