Effects of second milling time to the core loss of MnZn ferrites for high frequency application

The effect second milling time on the electromagnetic properties of MnZn ferrites has been studied up to MHz range. The average particle sizes of powder ranging from 1.49 to 1.16 μm were obtained by varying the second milling time from 72 to 324min. It is found that the total losses (Pcv) deteriorate when the second milling time over 252 min and the limit particle size is 1.21 μm. The value of initial permeability (μi) reduces by 20% when the particle size is 1.16 μm due to the uneven distribution of grain size, indicating that uniform microstructure demands suitable particle size. Meanwhile, the eddy current loss (Pe) and residual loss (Pr) dominate the total loss at 3 MHz playing a significant role in total losses. The hysteresis loss (Ph) and eddy current loss (Pe) deteriorate gradually at 3 MHz when the particle size is 1.21 μm at 100 °C. The residual loss increases greatly with the particle size decreasing at 3 MHz. An excellent MnZn power ferrite possessing high initial permeability (μi = 887), high saturation magnetic flux density (Bs = 531 mT) and low total losses (Pcv = 1940 kW/m3) at 3 MHz-50 mT is synthesized in this research.