Study Of Lead-Free X8R Ceramics Sintered At Medium Temperature

Multilayer ceramic capacitor （MLCC） is one of electronic components，which isvery important in electronic information technology now. BaTiO₃-based X8R，whichis a kind of MLCC，is studied widely and its products has been used to electroniccommunications，automotive electronics，aerospace and other industries. But nowmost of X8R ceramic materials contain heavy metal lead，which is greatly harmful toour health and our environment. In this paper，the effect of additives and preparingtechnology on dielectric properties of lead-free BaTiO₃-based X8R was investigated.On one hand，three kinds of additives （ MnCO₃，ZnO，Bi₂O₃ ） were added inBaTiO₃ ceramics，their effects on dielectric properties of system were studied.MnCO₃，which played a role of cosolvent，promoted the densification of ceramics andeffectively reduced lattice defects of the system, so dielectric loss of system wasdecreased. ZnO was helpful to the growth of crystalline grain and the spread ofimpurity ions in BaTiO₃ lattice，reduced the non-ferroelectric phase pore，so thedielectric constant of system was increased. Bi₂O₃ can form liquid phase in thesintering process，so it can reduced effectively sintering temperature and dielectricloss of system.On the other hand，the effects of preparing technology （ milling time，soakingtime，sintering temperature ） on dielectric properties of system were studied. Theresults indicated that increase of milling time can make Curie peak ofε-T curvedecrease，the dielectric constant of lower temperature greatly increased as increase ofsoaking time，and Curie point T_c shifted to higher temperature direction as rise ofsintering temperature. Through the proper adjustment of preparation technology of theceramics，the dielectric properties of the system were improved effectively. Whenmilling time is 200 min, sintering temperature is 1000℃and soaking time is 4 h, thedielectric properties of system are the best，ε≥2872.9，tanδ≤1.3%，|Δε/ε|≤15%，ρv≥1.8×10¹³Ω·mm，which are tested in 1 KHz.