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Ni‐Cu‐Zn ferrites with high Curie temperature for multilayer inductors with increased operating temperatures
Author(s) -
Reimann Timmy,
Capraro Beate,
Bartsch Heike,
Töpfer Jörg
Publication year - 2020
Publication title -
international journal of applied ceramic technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.4
H-Index - 57
eISSN - 1744-7402
pISSN - 1546-542X
DOI - 10.1111/ijac.13623
Subject(s) - materials science , sintering , ferrite (magnet) , curie temperature , shrinkage , ceramic , inductor , dielectric , composite material , metallurgy , ferromagnetism , optoelectronics , electrical engineering , condensed matter physics , physics , engineering , voltage
We studied the sintering behavior and magnetic properties of Ni 0.60‐y Cu y Zn 0.42 Fe 1.98 O 3.99 ferrites. The shrinkage is shifted toward lower temperature with increasing Cu content y. The addition of Bi 2 O 3 sintering aid induces enhanced shrinkage at T < 900°C and dense ceramics are obtained after sintering at 900°C. Such ferrites exhibit a permeability of µ = 135‐250 depending on the composition, sintering temperature and concentration of sintering additive. Ferrites with y = 0.20 show a high Curie temperature of T c = 307°C. Multilayer inductors were fabricated and cofired at 900°C using ferrite tapes without and with 0.75 wt% Bi 2 O 3 . The compatibility of ferrite tapes with different metal pastes (Ag, AgPd, and Au) was evaluated. Ferrite tapes were also integrated between layers of low‐ k dielectric CT708 tapes and successfully cofired at 900°C. Preliminary tests indicate that the multilayer inductors can be operated up to temperatures of 250°C. This demonstrates that high‐T c Ni‐Cu‐Zn ferrites are promising magnetic materials for inductive components for high operating temperatures.