Preparation And Dielectric Properties Of Barium Titanate Ceramics For Ultra-Thin Layer MLCCS

Barium titanate ceramic as the medium of multilayer ceramic capacitors（MLCC）,is the world’s largest use of chip electronic components,MLCC manufacturing technology also represents the level of a country’s electronics industry.At present,the international MLCC towards high-capacity,ultra-thin direction of rapid development,while China’s MLCC,especially ultra-thin layer MLCC preparation level is seriously backward,has become a constraint on the development of China’s electronics industry,one of the"neck"link.Therefore,for the application of ultra-thin layer MLCC,it is important to study the preparation technology of barium titanate nanocrystalline ceramics.The MLCC dielectric layer must be prepared from barium titanate nanopowder using the tape casting method to produce nanocrystalline ceramics.To address these special requirements,the process and the factors influencing each step from casting to reduction sintering are investigated,and the influence of the barium titanate raw material on the sintering and dielectric properties of the ceramics is discussed.In order to avoid the use of expensive nano-mills,a method for the preparation of slurry without ball milling was explored using highly dispersed hydrothermal nano-barium titanate powder as raw material.The effects of the composition of the cast slurry,the type of cast substrate,the type and addition of dispersant,the type and addition of solvent,the addition of binder and stirring time,the addition of plasticiser and ultrasonic stirring on the quality of cast film strips and billets were investigated.The surface of the dried billets is flat,dense and free of hollowness.The sintering technology of the cast billets was further investigated.It was found that when the sintering temperature did not exceed 1150°C,nanocrystalline barium titanate ceramics could be prepared,and the average grain size could be controlled below 180nm;when the sintering temperature increased above 1200°C,the relative density of barium titanate ceramics increases as the sintering temperature rises,but the grains of the barium titanate ceramics grew abnormally;the addition of an appropriate amount of Si O₂ could increase the relative density of the ceramics,reduce the grain size of the barium titanate ceramics,and make the surface of the barium titanate ceramics more stable.The effects of different barium titanate raw materials on the microstructure and properties of the ceramics were also studied and discussed.It was found that there were more microporous defects inside the hydrothermal barium titanate particles,which could not be eliminated even after heat treatment at 850°C,whereas there were no microporous defects inside the sol-gel titanate particles;the dielectric constant of ceramics fired in oxidising atmosphere with hydrothermal barium titanate was 1054.56 and the dielectric loss was 22.13,but the dielectric constant of ceramics fired in reducing atmosphere was 1200.32,but the dielectric loss is as high as 280.30,and the resistivity performance is seriously deteriorated,which may be related to the existence of more microporous defects in the raw material particles;the hydrothermal method of barium titanate is heat treated at 850°C for 1h,and the dielectric loss of its ceramics fired in the reducing atmosphere is still as high as 47.78;with the homemade sol-gel method of barium titanate as raw material,the dielectric constant of the ceramics fired in the reducing atmosphere is 307.04,the low dielectric constant should be related to the ceramic sintering density,but the dielectric loss is only 7.80 and there is almost no deterioration in resistivity properties.