Study On The Thick-film EMI Filter X7R Dielectric Ceramic

In this paper, the way of B-site substitution using precursor in (Ni1/3Nb2/3)O3-(Mn1/3Nb2/3)O3-BaTiO3 system was studied. On the basis of this system, X7R ceramics with prefect dielectric properties were achieved at intermediate temperature range. Meanwhile, the mechanics of precursor replacement of B-site ion was also discussed.The formation of some unexpected transition phase do harm to dielectric properties of system in sintering process, which can be avoided by doping with precursor in fine-grained BaTiO3. After substitution precursor for Ti4+, the Curie peak of Ba(Ni1/3Nb2/3)O3 and Ba(Mn 1/3Nb2/3)O3 were shifted to negative temperature. Moreover, the dielectric constant was improved greatly at room temperature because of the superposition effection. On the other hand, the average ionic radius of Ba(Ni1/3Nb2/3)O3 (0.0707nm)and Ba(Mn 1/3Nb2/3)O3 (0.0697nm)were similar and greater than Ti4+(0.061nm). The octahedron was enlarged after these big ions substituting partly for Ti4+. Other neighbor octahedrons can be compressed and the movement of Ti4+ in center was limited. To some extent, part of ferroelectricity was disappeared. This can reduce the dielectric constant, broaden the Curie peak and flatten the temperature dependence curve. The dielectric properties are as follow:ε≥5000 ΔC/C≤±15% (-55℃～+125℃) tgδ≤1.2% ρv≥1011Ω·cmThe flux was also used in order to reduce the sinter temperature to 1150℃. Under this sintering condition, cheaper electrode such as 70%Ag-30%Pd can be utilized to produce intermediate temperature sintered porcelain. This kind of material must be made good use of in EMI capacity filter. The dielectric properties in system are as follow:ε≥3600 ΔC/C≤±15% (-55℃～+125℃)tgδ≤1.2% ρv≥1012Ω·cm...