Effect of compressive stress on power loss of Mn–Zn ferrite for high-frequency applications

Abstract

In this work, the low-power-loss Mn–Zn ferrite was prepared by the traditional ceramic sintering process. This sample shows the good wide-temperature stability of power loss (Pcv). In the whole measurement temperature range of 25 - 120 °C, Pcvs maintain less than 100, 682, and 1455 kW/m3 at 100 kHz/100 mT, 500 kHz/100 mT and 800 kHz/100 mT, respectively. The effect of uniaxial compressive stress on power loss at 100, 500 and 800 kHz was investigated. Stress has greater impact on Pcv at high frequencies and Pcv increases remarkably. To clarify the mechanism of stress on power loss, Pcv was divided into three parts including hysteresis loss (Phv), eddy current loss (Pev) and residual loss (Prv), and the effect of stress on each part of loss was discussed. At the low frequency of 100 kHz, Pcv is mainly contributed by Phv. The applied stress leads the local anisotropic stress and makes domain wall displacement more difficult, which is the reason of the increase of Phv. When frequency increases to 500 and 800 kHz, Pev and Prv become more important. The compressive stress is in favour of electron transfer between Fe3+ and Fe2+ in grains and electron tunnelling effect at grain boundaries, which leads to the decrease of resistivity. This is the origin of enhanced Pev under the compressive stress. The enhanced Prv is related to the enhanced electronic diffusion under the compressive stress. The clarification of the mechanism of stress on power loss is beneficial to develop new soft ferrite materials with low stress sensitivity for high-frequency applications.