| BaTiO3has attracted wide attention because of its excellent dielectric and ferroelectric properties.In this paper,BaTiO3ceramics with high density and excellent dielectric properties were prepared by low-temperature cold sintering process.The effects of flux types,cold sintering process（sintering temperature,sintering time,uniaxial pressure）and annealing methods（traditional annealing and microwave annealing）on the structure,microstructure and properties of ceramics were investigated.The effect of powder treatment process（acetic acid concentration,treatment time,treatment temperature）on the densification of ceramic samples by cold sintering was studied.According to MLCC preparation process,multilayer BaTiO3ceramics were prepared by cold sintering process.The density,phase,microstructure and dielectric properties of the samples were characterized and analyzed,and the following conclusions were obtained:（1）BaTiO3ceramics with relative density of 95.39%were obtained by cold sintering100 nm BaTiO3powder at 400℃and 350 MPa for 1 h with Ba（OH）2·8H2O as flux,but the dielectric properties were low（<2000）.In order to improve the dielectric properties of the samples,the cold sintered ceramics were annealed at different temperatures.It was found that the ceramics annealed at 600℃could maintain a high tetragonal phase content and obtain a clear grain boundary microstructure.The annealed ceramics show good dielectric properties with relative density of 96.57%,dielectric constant of 3128,Curie temperature of 123℃and dielectric loss of 0.06.At the same time,the effects of cold sintering time and annealing time on the structure and properties of cold sintered ceramics are explored.It is found that prolonging the cold sintering time and annealing time can effectively reduce the generation of impurity phase.（2）In order to further improve the activity of BaTiO3powder,acetic acid was used to activate the powder and reduce some barium.Then,during cold sintering,Ba（OH）2·8H2O is used as flux to assist sintering,and barium is added,so that the ratio of barium to titanium can be adjusted and the problem of excessive barium caused by using Ba（OH）2·8H2O can be solved.At the same time,it can also solve the problem of the deterioration of dielectric properties caused by the introduction of K+and Na+when KOH-Na OH is used as flux.It is found that when the acetic acid concentration is too high,the particle size of the powder will increase,and the sintering barrier of the powder with large particle size will be high,which will reduce the sintering activity of the powder.The use of high concentration acetic acid will also lead to excessive acetic acid residue in the treated powder,which is not conducive to the dielectric properties of ceramics.At the same time,with the increase of powder activation temperature and activation time,the dielectric loss of ceramics will increase.Therefore,considering the performance and energy consumption of the sample,the optimum activation conditions of the powder are acetic acid concentration of 0.1 mol/L and 100℃/1h.The prepared ceramics have no barium-rich phase,which reduces the dielectric loss and improves the dielectric dispersion.The dielectric constant of the sample is 2987 and the dielectric loss is 0.04.（3）According to the MLCC preparation process,in order to prepare casting slurry with good stability and high solid content,we explored the effects of different dispersant and binder dosage on the slurry.It is found that when the dispersant is 4wt%and the binder is 10wt%,the slurry has the best performance and viscosity,and it is not easy to produce bubbles during casting.Ceramic capacitors with 30 dielectric layers were prepared by cold sintering process at 300℃and 50MPa.The thickness of each dielectric layer is 50μm.The electrode thickness is 5μm.After testing,the capacity range of the sample is0.46～0.52C/μF.The breakdown voltage range is 290～430V,and the average breakdown voltage is 364V. |
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