Study On High Electric Field Assisted Sintering Of Barium Titanate-Based Ceramics

Barium titanate?BaTiO₃?ceramics,with good piezoelectric and dielectric properties,are considered as the most potential lead-free piezoelectric ceramic materials and have been widely used in the sensors,ultrasonic transducer,micro displacement device,and other electronic components.However,according to the traditional solid phase sintering process,high temperature and long time were required to prepare dense BaTiO₃ ceramics.Therefore,the grain growth,which occurred during the sintering,was inevitable and also influenced the dielectric properties and thus application of the material.In recent years,flash sintering with the unique advantage of fast sintering inspired from the field assisted sintering provides a great potential of application prospect.In this study,with the controlling of heat treatment temperature,electric current density and holding time,barium titanate ceramics were fabricated via flash sintering.Then the effects of sintering parameters on the microstructure and dielectric properties of Ba TiO₃ceramics were characterized in detail.The results showed that some extra impure phases could be produced at the higher heat treatment temperature under the high electric field intensity applied.Also,the content of defects and pores,which distributed uniformly in the matrix,increased with the increase in heat treatment temperature,resulting in the decrease in density and irregular piezoelectric and dielectric properties for BaTi O₃ ceramics.In addition,the amount of defects and the degree of microstructure irregularity increased significantly with the increase of power density as well as heat treatment time,and the piezoelectric dielectric performance exhibited a decreased trend.Therefore,BaTiO₃ ceramics with Bi₂O₃ additive were prepared by liquid assisted sintering to improve the density and uniformity.The effects of the controlled heat treatment temperature,electric current density and holding time on microstructure and properties of the liquid assisted sintering of BaTiO₃ under the high electric field intensity were thus investigated.The results showed that the addition of Bi₂O₃ could delay the initial temperature of flash sintering as compared to single phase of BaTiO₃ under the high electric intensity.The grain growth of BaTiO₃ ceramics was not very apparent when the heat treatment temperature was below the flash point,while the grain growth became very significant when the heat treatment temperature exceeded the flash point.Moreover,Bi₂O₃doped BaTiO₃ ceramics with relative high piezoelectric and dielectric properties prepared by high electric field assisted sintering exhibited lower BaTiO₃ ceramics than those sintered in the traditional sintering furnace under the similar conditions.In addition,the increased holding time significantly reduced the density of Bi₂O₃ doped BaTiO₃ ceramic.The result also showed that the uniform microstructure could be achieved when the electric field intensity was 25V/mm.On the other hand,the effects of the controlled heat treatment temperature,current density,and holding time on the microstructure and properties of 1mol%Si₃N₄ doped Ba TiO₃ under the high electric field assisted sintering were investigated.The results showed that the grain size of samples exhibited no apparent change with the heat treatment temperature.Also,the higher input power is required to obtain higher density samples when Si₃N₄ is used as a sintering additive.In addition,the BaTiO₃-Si₃N₄ ceramics sintered with high electric field did not show a significant increase in the piezoelectric dielectric property.On the contrary,the BaTiO₃-Si₃N₄ ceramics exhibited a relative poorer performance with uneven piezoelectric properties due to the due to the relatively low relative density and inhomogeneity of microscopic microstructure.