Cobalt ferrite is a ferrimagnetic magnetostrictive ceramic that has potential application in magnetoelastic and magnetoelectric transducers. In this work, CoFe2O4 was obtained using a conventional ceramic method and Bi2O3 was used as additive in order to obtain liquid-phase sintered samples. Bi2O3 was added to the ferrite in amounts ranging from 0.25 mol% to 0.45 mol% and samples were sintered at 900 °C and 950 °C. It was observed the presence of Bi-containing particles in the microstructure of the sintered samples and the magnetostriction results indicated microstructural anisotropy. It was verified that it is possible to get dense cobalt ferrites, liquid-phase sintered, with relative densities higher than 90% and with magnetostriction values very close to samples sintered without additives.

Abstract-Pulsed-current sensors require transducers constituted of magnetic materials with high magnetic permeability in a frequency range compatible with the period and the frequency of the current pulse. The use of ferrites in this application has the advantage of low cost and low losses in high frequencies. The aim of this work is to present a procedure for selection of the ceramic processing route of Ni-Zn ferrite for application in a pulsed-current sensor. The ferrite samples were prepared under different processing parameters and characterized in terms of microstructure, chemical analysis, complex magnetic permeability, and magnetic hysteresis. The chosen processing route included high energy milling of the pre-sintered powder, its disaggregation before sample forming, and sintering of the samples in air for 2 h at 1300 • C. Tests were performed and it was verified that using this processing route for the fabrication of the sensor's core it was possible to monitor pulses of 0.1-1.0 µs.

No abstract

No abstract