Development of high-temperature high-permeability MnZn power ferrites for MHz application by Nb2O5 and TiO2 co-doping

Abstract MnZn power ferrites are technologically important for miniaturization and efficiency of electronic devices. It is of practical significance to obtain high working frequency and temperature in the MnZn ferrites. In this study, MnZn ferrites capable of working above 1 MHz and 80 °C have been successfully prepared by Nb2O5 and TiO2 doping. Nb2O5 promotes the densification process during sintering and exists as a resistive layer in the grain boundary region, leading to improved permeability and power losses. TiO2 doping results in the formation of localized Ti4+-Fe2+ pairs and offers extra cation vacancies for Nb5+ diffusion, which further enhances the effect of Nb2O5. The sample doped with 250 ppm of Nb2O5 and 2500 ppm of TiO2 presents optimal magnetic properties with the lowest power loss value of 394 kW/m3 at 1 MHz and 80 °C , along with an initial permeability of 1510, thus, serving as a good candidate for MHz, high-temperature and high-permeability power applications.