Preparation, Defects And Dielectric Properties Of Barium Titanate Nanopowders

MLCC is the cornerstone of electronic industry development and is called the "pillar of electronic ceramic industry".As the world’s largest and most rapidly developing electronic component,BaTiO₃ powder is required for the manufacturing of MLCCs.In-depth understanding of the effects of different defects of BaTiO₃ in terms of microstructure,morphology and dielectric properties can well help us to reasonably design BaTiO₃ powders that meet the requirements of dielectric properties.In this paper,in order to reveal the defect dipole configuration of BaTiO₃,compare the difference of defect content between domestic and foreign powders,and the effect of specific defect dipole configuration on the dielectric properties of BaTiO₃.The results of the full paper are as follows:（1）The OHO· containing tetragonal phase BaTiO₃ powder was prepared by hydrothermal method,which can promote the fine crystallization of ceramics when the OHO·content is low;when the OHO· content is high,the precrystallization of large particles appears on the surface while fine crystallization,which may be related to the enrichment of OHO·.Increasing the barium-titanium ratio can suppress the amount of OHO· generation,but the excessive Ba²⁺will also introduce BaCO₃ impurities in the product,so choosing a suitable barium-titanium ratio（2:1）can both control the content of OHO· and reduce the generation of BaCO₃ impurities.（2）A BaTiO₃ with hollow spherical shape was prepared,and its OHO· content reached 34.76%after characterization.A OHO· induced（200）crystallographic orientation phenomenon was reported.The defect composition and evolution of BaTiO₃ powders containing OHO· were investigated,and it was found that there existed 2OHO·-VBa",defect dipole configurations,and after calcination or sintering steps,OHO· would transform to V_o^¨and the defect dipole configuration would evolve to V_o^¨-VBa".（3）The effects of different preparation methods on the V_o^¨ of BaTiO₃ were investigated experimentally.It was found that changing the preparation method or adjusting the experimental parameters（Ba/Ti,pH,reaction temperature,reaction time,etc.）did not have any significant effect on the regulation of V_o^¨.The use of different atmospheres for sintering BaTiO₃,on the other hand,successfully regulated the V_o^¨.BaTiO₃ sintered in air atmosphere had no obvious defects,while BaTiO₃ sintered under low oxygen partial pressure conditions had a large amount of V_o^¨ The BaTiO₃ sintered in 100%Ar atmosphere mainly existed in the form of V_o^¨-VBa" ion compensation;the BaTiO₃ sintered in 1%H2&99%Ar atmosphere mainly existed in the form of V_o^¨-2Ti’_Ti electron compensation.（4）We found that the V_o^"-2Ti’_Ti defective dipole configuration affects the cell structure of tetragonal phase BaTiO₃ and there is a tendency to shift from tetragonal phase to cubic phase,while the V_o^¨-VBa" defective dipole configuration hardly affects the cell structure of tetragonal phase BaTiO₃.A giant dielectric phenomenon caused by the V_o^¨2Ti’_Ti defect dipole configuration is reported,with a room temperature relative constant（εr）up to 3.8×10⁵ and a Curie temperature relative permittivity（εTc）up to 5×10⁵ at frequencies as low as 1 kHz,along with a dielectric loss tanδ of 10%.As the frequency increases,εr decreases and tanδ increases.When the frequency is up to 200 kHz,εr reaches a minimum of 1 × 10⁵ and tanδ is up to 80%.