Electrical properties of low-temperature-fired ferrite-dielectric composites

The effects of the BaO center dot(Nd0.8Bi0.2)(2)O-3 center dot 4TiO(2) (BNBT) to NiCuZn ferrite ratio and addition of Bi2O3-B2O3-SiO2-ZnO (BBSZ) glass on the sintering behavior, microstructure evolution, dielectric and magnetic properties of BNBT-NiCuZn ferrite composites were investigated in developing low-temperature-fired composites for high frequency electromagnetic interference (EMI) devices. The results indicate that these composites can be densified at 900 degrees C and exhibit superior dielectric and magnetic properties with the addition of BBSZ glass. The dielectric system used in the ferrite-dielectric composites reported in the previous studies mostly belong to the ferroelectricity group, which are not suitable for use in the high frequency range (> 800 MHz) due to the selfresonance frequency limit. In this study, the dielectric constant remains nearly a constant over a wide range of frequencies (100 MHz to 1 GHz) and the magnetic resonance frequencies are larger than 100 MHz for the BNBT + BBSZ glass-NiCuZn ferrite composites. Therefore, the BNBT + BBSZ glass-NiCuZn ferrite composites can be a good candidate material for high frequency EMI device applications. (C) 2008 Elsevier Ltd and Techna Group S.r.l. All rights reserved.