Ferrite-based material as a permanent magnet for components of electrical generators

Perdamean Sebayang, Muljadi Masbah, R T Siregar and Tomi Budi Walyo

Abstract

A permanent magnet based on ferrite for use as components of electrical generators has been fabricated by two different methods: solid–solid mixing and cooprecipitation. The conventional solid–solid mixing method uses Fe₂O₃ and BaCO₃ as starting materials with mole ratio n=BaO:Fe₂O₃=1: 6. The mixture is calcinated at 1100 °C and two crystal structures, BaOFe₂O₃ and BaFe₁₂O₁₉, were obtained with particle size of about 0.5–1.5 μm. Sintering at 1100 °C was followed by a magnetization process. Measurements give the following physical parameter values: remanence, Br=0.0792 T; magnetic saturation, Bs=1.21 T; coersivity, Hc=44.7 kA m^-1; density 3.43 g cm^-3 and porosity 9.16%. On the other hand, the cooprecipitation method uses FeCl₃ and BaCl₂ solution with mole ratio n=BaCl₂:FeCl₃=1:6. After the calcination at 900 °C and higher temperatures a single crystal structure of BaO6Fe₂O₃ is formed with particle size of about 30–60 nm. The optimum sintering temperature for the formation of this single phase crystal structure is 1050 °C. The physical parameters of the final product have the following values: Br=0.2673 T; Bs=1.42 T; Hc=89.4 kA m^-1; density 4.34 g cm^-3 and porosity 3.36%