Synthesis Of Barium Titanate In Nanoscale From Hydrothermal Process Assisted By Ionic Liquids

Nano-BaTiO₃ known as“the pillar of the electronic ceramic industry”is widely used in thermistors?PTCR?,multilayer ceramic capacitors?MLCC?,ultrasonic detectors,temperature sensors,dynamic random access memory?DRAM?and other electronic components.In recent years,electronic information technology has gradually grown toward integration,intelligence,and miniaturization.It has proposed the requirements for electronic components with multilayer type,solid state,multi functionalization,high stability,and high reliability to meet needs of development.And the key is the ceramic materials with ultrafine particles,high purity and uniformization.Therefore,it is also a research focus to explore the method to prepare BaTiO₃ powders which has high purity and ultrafine particles and can be produced in large scale.In this paper,spherical BaTiO₃ was prepared by hydrothermal method using Ba?OH?₂·8H₂O and TiO₂ as raw materials.The effects of reaction conditions on the content of tetragonal phase in BaTiO₃ were investigated,and a series of characterizations were performed.The results showed that nano BaTiO₃ has the highest tetragonal phase content,axis ratio c/a can reach 1.0086,and tetragonal phase content is 95%when the concentration of Ba?OH?₂·8H₂O was 1.5 mol/L,the molar ratio of Ba/Ti was 2.5/1,the reaction temperature was 200°C,reaction time was 48 hours,and 9.7 mL/g _TiO2 ammonia water was added into the system.Nano BaTiO₃-IL can be obtained via hydrothermal process assisted by ionic liquids,and crystal structure,structure and morphology were characterized.The results showed that the average grain size of the nano BaTiO₃-IL obtained was only 34 nm when the concentration of Ba?OH?₂·8H₂O was 1.5 mol/L,the molar ratio of Ba/Ti was 2.5/1,the reaction temperature was 200°C,reaction time was 48 hours,the mass of[Tmospmim]Cl ionic liquid was 5 g,and 9.7 mL/g _TiO2 ammonia was added into the system.The crystal structure of the nano BaTiO₃-IL with the addition of ionic liquid is cubic phases,but the average grain size of that is greatly reduced.The reasons for that are as follows:the ionic liquid can reduce the surface tension of the solution and enhance the solubility of Ba?OH?₂·8H₂O;ionic liquids with high viscosity coefficient can affect the bulk diffusion and surface transport of Ba?OH?₂·8H₂O in the system,which will reduce the diffusion rate of the materials,restrict the flow of reactants and the reaction was conducted in a certain area.The properties above of ionic liquids accelerate the nucleation rate and decrease the growth rate of BaTiO₃.And the nucleation rate of BaTiO₃ is greater than the growth rate,so the average grain size of BaTiO₃-IL obtained is small.The electrical properties of nano BaTiO₃ with different tetragonal phase content and different crystallite size were studied.The results show that the dielectric constant of BaTiO₃ceramics increases with the increase of the content of tetragonal phase,and the dielectric constant of BaTiO₃ ceramics decreases with the decrease of grain size in the fine grain range.