In this study, the cofiring behavior and interfacial interaction between a low dielectric constant LTCC material and NiCuZn ferrites at 900°C were studied using XRD, dilatometer, SEM, EPMA and TEM. It was observed that the delamination occurred at the interface between LTCC and NiCuZn ferrites added with Bi2O3. It may be due to the Bi enriched at the interface and diffused into LTCC, which shifted the densification curve of LTCC towards low temperature, and hence resulted in the shrinkage mismatch between LTCC and NiCuZn ferrites.

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The effects of cobalt oxide addition on the microstructure and electrical properties of CuZn ferrites were investigated. CuZn ferrites with compositions of (CuO)0.2(ZnO)0.8(Co3O4)x/3 (Fe2O3) 0.986-2x; x = 0 , 0.02, 0.04, 0.08, 0.1 were synthesized using a solid state reaction. It was observed that the addition of cobalt will change the amounts and distribution of Cu2+, Cu+, Fe2+, and Fe3+ in the grain and grain boundary. The segregation of copper ions at the grain boundary was observed as the substitution of cobalt was increased. Moreover, as the x value was increased above 0.04, second phases of CuO and ZnO were found. The different amounts and distribution of Cu2+, Cu+, Fe2+, and Fe3+ in the bulk and grain boundary for samples added with different amounts of cobalt changed the conductivity activation energies of the bulk and grain boundary, and hence affected the space polarization and dielectric properties.