Preparation and electromagnetic properties of low-temperature sintered ferroelectric-ferrite composite ceramics

For the purpose of multilayer chip EMI filters, the new ferroelectric-ferrite composite ceramics were prepared by mixing PMZNT relaxor ferroelectric powder with composition of 0.85Pb(Mg1/3Nb2/3)O-3-0.1Pb(Ni1/3Nb2/3)O-3-0.05PbTiO(3) and NiCuZn ferrite powder with composition of (Ni0.20Cu0.20Zn0.60)O(Fe2O3)(0.97) at low sintering temperatures. A small amount of Bi2O3 was added to low sintering temperature. Consequently, the dense composite ceramics were obtained at relative low sintering temperatures, which were lower than 940degreesC. The X-ray diffractometer (XRD) identifications showed that the sintered ceramics retained the presence of distinct ferroelectric and ferrite phases. The sintering studies and scanning electron microscope (SEM) observations revealed that the co-existed two phases affect the sintering behavior and grain growth of components. The electromagnetic properties, such as dielectric constant and initial permeability, change continuously between those of two components. Thus, the low-temperature sintered ferroelectric-ferrite composite ceramics with tunable electromagnetic properties were prepared by adjusting the relative content of two components. These materials can be used for multilayer chip EMI filters with various properties. (C) 2003 Elsevier B.V. All rights reserved.