Manganese zinc ferrite with high initial permeability - contains silica which increases density and reduces electric losses

摘要

has intial permeability (mu 1) 900-1600, low losses, and is usable at up to 1 MHz. The starting materials (a) are of usual commercial purity, and contain in mole %: 50-55% Fe2O3, 10-40% MnO, and the rest ZnO; plus by wt. 0.06-1%, esp. 0.06-0.8% CaO and 0.006-0.03%, esp. 0.01-0.015% SiO2; and up to 5 mole % of the Fe2O3 can be replaced by SnO2 and/or TiO2. The ferrite may also contain 0.03-0.5 wt.% CoO; and materials (a) may contain 0.05-0.35 wt.% SiO2, but the pref. ferrite has a total of 0.036-0.04% SiO2. The esp. pref. ferrite starting materials have compsn. (Z) in mole %: 52.2% Fe2O3, 32% MnO, 14.2% ZnO, 0.5% SnO2, 1.1% TiO2, with 0.04 wt.% SiO2. The mixt. (Z) is opt. presintered at 850 degrees C; mixed with 0.1 wt.% CaCO3; wet milled; dried; passed into blanks; heated in N2 to 1150-1200 degrees C. for sintering in N2 contg. a little O2; and then cooled in an atmos. contg. a decreasing amt. of O2. The use of commercial materials (a) with the % SiO2 stated reduces the cost of the ferrites and also provides a high density and low losses.