Study On The Manufacture And Dielectric Property Of NBT Based Multilayer Ceramic Capacitor

Capacitors utilized in some specific fields such as aerospace and oil drilling were urged to study the dielectric materials using in high temperature.It seemed that multilayer ceramic capacitors?MLCCs?satisfying X9R standard of Electronic Industries Association?EIA?or working at broaden temperature range were seriously necessary.Critical techniques for producing MLCCs using in high temperature were controlled tightly overseas.Few studies about the applications of(Na_0.5Bi_0.5)TiO₃?NBT?based ceramics in MLCC field were reported.Therefore,this paper tried to improve the dielectric temperature stability of NBT based ceramics by adding NaNbO₃?NN?phase to satisfy EIA X9R.The preparation technologies of NBT based MLCC were investigated to finally fabricate MLCCs meeting the EIA X9R requirement.Oxides were doped into the NBT-NN ceramic to enhance the insulation resistivity for the Ni-MLCC application.?1-x?NBT-xNN ceramic system was investigated with good dielectric temperature stability.In this paper,?1-x?NBT-xNN?x=0.2,0.3,0.4,0.5,0.6?ceramic were synthesized by solid state reaction method.The effects of NN phase on the structure and dielectric properties of NBT ceramic were discussed.The results showed that,with addition of NN,the ceramic became more obvious ferroelectric relaxor.The dielectric temperature stability of NBT ceramic was improved with certain addition of NN.The P-E loops of the ceramics tended to be slimmer with addition of certain NN.Then the energy storage density of ceramics were enhanced.The0.6NBT-0.4NNceramicwasinvestigatedwithdielectric constant?800-1000?,dielectric loss?<1%?and capacitance variation?<11%?in the temperature range of-55-205?.The complicated MLCC preparation technology was vunerable to be involved with each process conditions,especially tape casting,lamilating,inner electrode printing,burning out and sintering procedures.It would result in the different dielectric properties of MLCCs.Therefore,the tape casting process of NBT based ceramics was investigated.Different burning out and sintering procedures were designed to investigate the microstructure and dielectric properties of MLCCs.The results showed that the burning out rate of MLCC devices should be as slow as possible and the sintering rate of MLCC should be suitable.Because of fast heating rate,the inner electrodes of MLCCs seemed to be less continuous.The dielectric properties of MLCCs also were involved with slow heating rate.MLCCs of0.6NBT-0.4NN ceramic were investigated with dielectric constant?800-1000?,dielectric loss?<1%?,satisfying the EIA X9R standard in the temperature range of-55-205?.0.6NBT-0.4NN ceramic was investigated with good dielectric temperature stability,but poor resistance in reducing atmosphere.MnO₂,MgO and Y₂O₃ oxides were respectively doped into 0.6NBT-0.4NN ceramic.The phase structure,dielectric properties and insulation resistivity of the ceramics were studied.The results showed that the capacitance variation at high temperature of 0.6NBT-0.4NN ceramic doped with MnO₂,MgO and Y₂O₃ would increase decreasing the dielectric temperature stability of the ceramic and the insulation resistivity increased with the leakage current decrease.The ceramic compositions of?1-x?[0.6NBT-0.4NN]-xMnO₂?x=0.015,0.025?,?1-x?[0.6NBT-0.4NN]-xMgO?x=0.005,0.007?and?1-x?[0.6NBT-0.4NN]-xY₂O₃?x=0.003,0.005,0.01?were investigated with good performances satisfying EIA X9R standard at 1kHz.