Abstract
A MnZn ferrite material with larger electrical resistance, which can be used in high frequency region exceeding 1 MHz, is investigated. The MnZn ferrite material with iron defect in the composition comprises the following basic components: 48.6 mol% Fe2O3, 24.2 mol% ZnO, 25.2 mol% MnO, and the remainder being TiO2 and SnO2. By the addition of TiO2 and SnO2, even if the ferrite material is sintered in air, electrical resistance of 103 times that of the conventional MnZn ferrite can be obtained, and high initial permeability of 350 to 500 as estimated can be secured even at high frequency of 5 MHz. It is well known that Sn and Ti receive electrons from Fe3+ to form Fe2+. Since many Sn4+ and Ti4+ having the stable number of valency are present, exchange of electrons between Fe3+ and Fe2+ are substantially inhibited, and as a result, electrical resistance far larger than the conventional one (about 103 times) can be obtained. This kind of ferrite material is suitable for switching power supply, a rotary transformer, choke coils, electronic parts such as for various kind of inductance elements and impedance elements for countermeasure against EMI, or for electromagnetic absorbers.
