Influences of High Calcination Temperature on Densification and Magnetic Properties of Low-Temperature-Fired NiCuZn Ferrites
Traditional low-temperature-fired NiCuZn ferrites (900 °C sintered) were generally prepared at relatively low calcination temperatures to increase the activity of the calcined powders and promote sintering. However, in this study, we changed the calcination temperature from 700 °C to 1000 °C to investigate the influences of high calcination temperature on the densification characteristic and magnetic properties of the low-temperature-fired NiCuZn ferrites. It was found that although a high calcination temperature decreased the activity of the calcined powder, the NiCuZn ferrite could attain a higher sintered density with an adequate sintering aid. Furthermore, a uniform microstructure with small average grain size was obtained for the sample calcined at 1000 °C with 1 wt% Bi2O3 sintering aid. It also displayed high performances on Q-factor and permeability. Hence, choosing a high calcination temperature and adding more sintering aid was also an option for obtaining high performance and low-temperature-fired NiCuZn ferrites.
Magnetic properties and sintering characteristics of NiZn(Ag, Cu) ferrite for LTCC applications
Abstract For applying low-temperature co-fired ceramics technology to ferrite with Ag electrode, Ni 0.2 Zn 0.5 Cu 0.3 ferrite nanopowders with AgO contents of 0, 0.1 and 1 wt% were synthesized using metal nitrates. Thick films fabricated by a doctor blade method were sintered for 72 h at different temperatures (925, 900, 875, 850 °C). As a result, the saturation magnetization, coercivity and permeability of Ni 0.2 Zn 0.5 Cu 0.3 ferrite with AgO contents of 0.1 wt% at a sintering temperature of 875 °C were 4.05 kG, 4 Oe and 521, respectively, which were close to those of bulk NiZn ferrite.
The infrared absorption and dielectric properties of Li–Ga ferrite
Abstract The investigated compositions of the Li–Ga ferrite system Li 0.5 Fe 2.5− x Ga x O 4 (where x  = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) were studied by means of infrared (IR) spectroscopy. The analysis of IR spectra indicates the presence of splitting in the absorption band due to the presence of Fe 2+ ions in ferrite. The dielectric constant ɛ ′, the dielectric loss ɛ ″ and the loss tangent tan  δ were measured at elevated temperatures ranging from room temperature up to 850 K as a function of frequency ( f  = 10 2 –10 6  Hz) for the investigated compositions. Maximum peak in tan  δ and inverse peaks in ɛ ′ appeared for some samples due to the resonance phenomenon. The obtained data were discussed based on the valence exchange between (Fe 3+ and Fe 2+ ) and (Ga 3+ and Ga 2+ ), i.e. hopping mechanism.