The Low-temperature Cofiring Properties Of Ferroelectrics/NiZn Ferrite Multilayer Composite

Recently,the surface mount technology (SMT) has been rapidly developed for miniaturization of electric devices such as multilayer ceramic capacitor (MLCC) and multilayer chip inductor (MLCI). Multilayer chip LC filter (MLLC),which is combined with several capacitors and inductors by the production process of multilayer chip components,is a type of advanced surface mount devices (SMD). Lead based relaxor ferroelectrics,and NiCuZn ferrite are promising materials for the multilayer chip LC filters. The key issue of manufacturing multilayer chip LC filters is cofiring the capacitors and inductors together at low temperature. In the present study,the multilayer components were prepared by cofiring Pb(Ni1/3Nb2/3)O3-PbTiO3 (abbreviated as PNN-PT) based ferroelectrics and NiCuZn ferrite. The cofiring properties and interfacial interactions such as chemical reaction,ionic interdiffusion between the constituents were investigated.Firstly,the rules of choosing dielectric material for Multilayer chip LC filter are proposed. According to the rules,0.8Pb(Ni1/3Nb2/3)O3-0.2PbTiO3 (0.8PNN-0.2PT) ceramic was chosen as the basis dielectric material. W03 and CuO were added into it to lower the sintering temperature. The phase structure and dielectric properties were investigated. The results show that CuO can not decrease the sintering temperature effectively as WO3 can do. The low-temperature-sintered PNN-PT-based ceramics with excellent dielectric properties are successfully prepared.Secondly,the multilayer components were prepared by cofiring PNN-PT-based ferroelectrics and (Ni0.5Cu0.4Zn0.1)Fe2O4 ferrite. The interaction,cofiring properties,camber development,and interface microstructure were investigated. The results show that there is no chemical reaction between the ferroelectrics and ferrite materials. The camber of the composites was observed at the cofiring temperature range from 800C to 950C. It shows that the grain of ferroelectrics adjacent to the interface is larger than that far from the interface. The difference factor dD is proposed to describe the microstructure difference between the interface and the inner parts. The difference factor decreases with increasing sintering temperature from 800 C to 900C.The camber development mechanism and the influence factors were researched by geometry analysis,viscous analysis and sintering kinetics analysis. The camber model was established and the equation for calculating curvature of camber was proposed. The influence factors for camber involve the original size of composite,the sintering properties and the shrinkage mismatch between the two materials. The more the shrinkage mismatch is,the larger the curvature is. The calculated results are in agreement with the experimental results.Thirdly,the cofired materials were adjusted according to the analysis of camber mechanism. The densification kinetics of the new cofiring system was thoroughly investigated and the apparent activation energy of sintering was calculated. The results show that the sintering mechanism of PNN-PT-based low-temperature-sintered ceramics (JD) is controlled not only by grain lattice diffusion,but also by grain boundary diffusion. The sintering mechanism of (Ni0.8Cu0.12Zn0.12)Fe1.96O4 ferrite material (TY) is mainly controlled by grain boundary diffusion. The apparent activation energy of JD and TY materials are 162 - 174KJ/mol and 208 - 235 KJ/mol,respectively. After these researches,the equations for densification kinetics of JD and TY materials are established.The effect of sintering time on the phase structure and microstructure was also investigated. It reveals that the perovskite phase of JD material decreases with increasing sintering time. The sintering time has no effect on the phase structure of TY ferrite. The grain size of both JD ferroelectrics and TY ferrite increases with increasing sintering time. 2 hours is the best sintering time.The multilayer composites (COF3#) were prepared at 900 C by cofiring JD ferroelectrics and TY ferrite using tape casting processes. The micros...