Microstructure and properties of commercial grade manganese zinc ferrites

Abstract

The microstructures of differently processed Commercial grade MnZn soft ferrites have been studied using transmission electron microscopy and microanalysis, and the microstructural features correlated with the magnetic properties. Special emphasis has been placed on the grain boundaries. The permeabilities range frOm 1200 to 18,000 and loss factors (tan5/p) from 1.0 x 106 to 13.7 x 106 at 50 kHz. The pore distribution in these ferrites was quite diverse although the total porosities are nearly the same. In specimens of low i either the defect density was high or varying amounts of amorphous phase were observed at the grain boundaries. In these samples STEM X-ray analyses revealed the presence of Ca and Si in the thin grain boundary phase Also, in some specimens the presence of Fe20 3 and/or Mn0 2 precipitates at some grain junctions was observed In the high p ferrites, few defects and no intergranular ohases were observed, and Ca 12 could not be detected It is suggested that the lattice distortion associated with the amorphous phase and the boundary seqregation reduces the permeability.

Mechanism of Core Loss and the Grain-Boundary Structure of Niobium-Doped Manganese–Zinc Ferrite

“…8 as a function of frequency. Initial permeability of sample B was about 15% smaller than that of sample A compatible with the result of Tsunekawa et al (4), where the lattice parameter increases near the grain boundary and the resonance frequency due to the resonance of domain wall motion and/or spin rotation became higher by due to the incorporation of Ca atoms in the spinel lattice.…”

Influence of the Addition of Bi2O3 on the Grain Growth and Magnetic Permeability of MnZn Ferrites

“…7,8 Studies of the grain boundary chemistry in combination with grain boundary structural analyses revealed that the grain boundaries are usually a source of stress originating from ZnO evaporation, 9 the presence of a glassy phase on the grain boundary, 10 and segregation of aliovalent ions. 11,12 Microstructural studies of MnZn ferrites showed that not all microstructures composed of grains with overestimated grain size and trapped porosity deteriorate the magnetic permeability of highly permeable MnZn ferrites. Particularly in samples where the pore-to-pore distance is relatively large, the magnetic permeability may lead to a pronounced secondary permeability maximum (SPM) with relatively high permeabilities.…”

An analysis of Mn-Zn ferrite microstructure by impedance spectroscopy, scanning transmission electron microscopy and energy dispersion spectrometry characterizations

“…So, it should also be noted that the static dielectric constant of boundary layers are quite different from the bulk grains. In fact, Ca oxides contained in the powder are know to segregate under impurities forms in the boundary regions, producing at these places magnetic and dielectric properties far from that of ferrite crystallites 17,18,19 . Since the ferrite impedance is modelled by series resistance-capacitance elements, the anomalously high apparent dielectric constant of ferrites is a consequence of the high capacitance of the thin boundary regions connected in series by highly conductive bulk grains.…”