Influence of Microstructure on the DC-Bias-Superposition Characteristics of NiZn Ferrites

The influence of microstructure on the magnetic properties, especially the dc-bias-superposition characteristics, of NiZn ferrites has been investigated. The value of saturation magnetic flux density (
B
_s
) first increased and then changed little with variation of the sintered density, and showed little relation to the microstructure. Coercivity (
H
_c
) decreased continuously with increasing average grain size. Δ
B
(
B
_s
-remanence) first increased with increasing average grain size, but then gradually decreased when abnormal grain growth prevailed. The incremental permeability (permeability with magnetic field superposition) was influenced by both Δ
B
and
H
_c
. A sample with higher Δ
B
and
H
_c
favored the attainment of a higher incremental permeability. The
Q
-factor was mainly determined by the sintered density and microstructure. To sum up, a uniform and dense microstructure with relatively small average grain size is favorable for obtaining better dc-bias-superposition characteristics, including permeability and
Q
-factor.