Synthesis And Characterization Of BaTiO₃ Nanoparticles In Microemulsion

Barium titanate(BaTiO₃)is a material with excellent performances of ferroelectric and dielectric,and has been widely applicated in PTCR,MLCC,DRAM and other optoelectronic devices.As the development in micro electronic industry,the requirement of electronic devices is greater and greater.And the devices need to be smaller,lighter,thinner and muti-functions with high dependability and stability.So the raw powders should be ultrathin,uniform with high performance and stability. Moreover,giving full play to the excellent properties of nano devices needs efficient assembly methods which form the nano materials to specific array or system.And this may require the nano materials have high consistence on size and morphology. Especially in Langrnuir-Blodgett(LB)assembly system,the materials should be highly dispersed and uniform.Therefore,research on synthesizing of ultrathin, uniform BaTiO₃ particles with high purity and low aggregation has important significance.In reverse microemulsion system,the reverse micelles are used as "micro reactors",which could restrict the processes of nanoparticles' nucleation,crystal growth and coalescence.These "micro reactors" could control the particles' size and shape conveniently.As a result,size controllable BaTiO₃ nanoparticles can be synthesized in microemulsion.Because of the coating surfactant on the particles surface,which could effectively inhibit agglomeration,nanoparticles are highly dispersed,even monodispersed.In this paper,we use reverse microemulsion method to synthesize Barium titanate nanoparticles.BaTiO₃ nanoparticles were synthesized in microemulsions consisting of water,OP-10,hexanol and cyclohexane,in which Ba(OH)₂·8H₂O and tetrabutyl titanate were used as starting reactants.Influences of reacting temperature,the concentration of reactants and surfactant,molar ratio of water to surfactant on the synthetic reaction were studied.Then the obtained products were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM), high-resolution transmission electron microscopy(HRTEM)and Raman scattering spectra.Finally,the optimum process conditions of the product synthesis were obtained.Furthermore,the products were washed by acetic acid under ultrasonic condition,and then pure BaTiO₃ nanoparticles were acquired.In addition,BaTiO₃ nanoparticles prepared by hydrothermal microemulsion method and ultrasonic microemulsion method were investigated in this paper.And the samples were compared with the ones by direct reverse microemulsion method.The phase of BaTiO₃ nanoparticles at room temperature,either cubic or tetragonal,is a controversial problem for a long time.In this paper,the obtained nanoparticles in microemulsions were characterized by Raman scattering spectra in order to study the phases of the particles.As a result,the prepared particles are mixed crystal structure with both cubic and tetragonal phase.The influence of heat-treatment on the particles was also discussed in this paper.