Influence Of Li Addition On The Magnetic Performance And Microstructure Of MnZn Ferrite

With the development of miniaturization and high efficiency of electronic devices,as well as the concept of energy saving,lots of efforts have been exerted to produce switching power supply with smaller size and higher conversion rate.To obtain high performances such as higher initial permeability,higher saturation magnetization,and relatively lower power loss is very important.But at the same time to achieve this goal is very difficult.This study of MnZn ferrite with high saturation flux density and low loss at high temperature is based on previous experimental and theoretical research,Samples were prepared by the standard ceramic process.This paper is devoted to study the effects of Li addition,particle size distribution,sintering atmosphere and drying process on the microstructure and properties of MnZn ferrite.The experiments find that with increasing the amount of Fe2O3,the saturation flux density increases and the temperature corresponding to the minimum power loss decreases.Moreover,the effect of Li addition is converse.In addition,we also found that as the oxygen partial pressure increases from 0.35%to 0.75%,the minimum power loss values of MnZn ferrite decreases gradually and the temperature corresponding to the minimum power loss values decreases slowly.But as the oxygen partial pressure increases from 0.75%to 1.9%,the minimum power loss values of MnZn ferrite decreases little and the temperature corresponding to the minimum power loss values increases by about 10?.We studied samples sintered in equilibrium sintering atmosphere of Po2=1.9%,samples sintered in equilibrium sintering atmosphere of Po2=0.75%,and samples sintered in sintering atmosphere of Po2=3.5%in the soaking stage and cooled in equilibrium sintering atmosphere of Po2=0.75%.Samples using powders of bigger particle size and sintered in sintering atmosphere of Po2=3.5%+0.75%have higher saturation magnetization and relatively lower power loss,while,the performances of samples using powders of the least particle size changed little.Furthermore,the temperatures corresponding to the minimum power loss values of samples sintered in sintering atmosphere of Po2=3.5%+0.75%and Po2=0.75%are higher by 10? than samples sintered in sintering atmosphere of Po2= 1.9%.Influence of Ca addition on the performances of MnZn ferrites using powders of different particle size was also investigated.It was found that the optimal amount of Ca addition is varied as the particle size of starting powder changes.Last but not least,the drying process can affects the characteristic of loss and temperature.Excessive drying time leads to a reduction of Li in the spinel structure,finally temperatures corresponding to the minimum power loss values of MnZn ferrite increase as a result.