Development of a Low Loss Mn-Zn Ferrite Material for High Frequency Applications

Abstract

Ceramic ferrites are magnetic materials composed of selected oxides with iron oxides. The most common commercial soft magnetic materials are Mn-Zn ferrites, having general formula AB2O4. The Manganese-Zinc ferrite is preferred for lower frequency applications generally for power transformers, power inductors and general power applications. With the advance of modern electronic technology, there has been a critical need for Mn-Zn ferrites with lower power loss at higher frequencies. In keeping with the current demand for size reduction of electronic equipment, more power-saving electronic devices and more efficient switched-mode power supplies has received considerable attention. Power supplies being an integral part of electronic equipments from computers and microprocessors to TV and video tape-recorders, the demand for ferrites cores, which are an essential component of the switching power supplies, has increased. In the present work, attempts have been made to reduce the power loss at high frequency, its variation with temperature in Mn-Zn ferrites, using traces of additives. The effect of these additives on the electrical and magnetic properties is studied intensively. In this project, Mn- Zn ferrite cores of the basic composition of 52.5 mole % Fe2O3, 41.2 mole % MnO and 6.3 mole % ZnO have been synthesized by conventional ceramic route. These ferrites have been investigated for their electrical and magnetic properties such as saturation magnetization, initial permeability, Curie temperature, resistivity and dielectric loss between 0.5MHz-3MHz. The minimum power loss of the Mn-Zn ferrite is 137 Kw/m3 at 100 KHz, 80oC and 100 mT, and of 309 Kw/m3 at 200 KHz, 100oC and100 mT.