Studies Of The Preparation And Dielectric Properties Of CaCu₃Ti₄O₁₂ Doping/Composite Ceramic Materials

The calcium copper titanate material(Ca Cu₃Ti₄O₁₂,referred to as CCTO)is a body-centered cubic perovskite structure,in which the Ti atom is located at the body center of the oxygen octahedron,and Ca²⁺and Cu²⁺occupy the eight vertices of the octahedron with a ratio of 1:3,respectively.Cu²⁺and adjacent four O^2-to form Cu O₄square plane coordination.The Ti O₆ octahedron thus formed is connected with the adjacent six different Cu O₄,which makes the Ti O₆ octahedron tilt.Calcium copper titanate has the characteristics of high dielectric constant（up to 10⁴ at 1 k Hz and at room temperature）,good temperature stability,etc.,and has a wide range of application prospects in electronic components such as memory and filters.However,the higher dielectric loss of CCTO materials also limits its further practicality.Therefore,it is an important research direction to find a method that can not only maintain the high dielectric constant of CCTO material but also reduce its dielectric loss.Since the dielectric properties of CCTO are extrinsic factors,doping cations or composite oxides to modify its microstructure is a common modification method.In this study,the cationic doping(Sr²⁺,Zr⁴⁺)and composite oxide（Sr Ti O₃）modification experiments were carried out on copper calcium titanate materials by the improved sol-gel method.The effects of doping concentration and sintering temperature on the dielectric properties of the materials were studied.The effects of cation doping and oxide composite on the crystal structure and dielectric properties of CCTO materials were specifically studied by means of X-ray diffraction（XRD）,scanning electron microscope（SEM）and other testing instruments.The main research contents and conclusions involved in this paper are as follows:（1）Sr²⁺doped CCTO ceramic material:the dielectric loss（tanδ）of the composite ceramic material sintered at 1000°C in a very wide frequency（20 Hz-100k Hz）range can be lower than 0.05.The dielectric loss（tanδ）of Ca_0.9Sr_0.1Cu₃Ti₄O₁₂ceramic is as low as 0.008 at 300 Hz.The Ca_0.8Sr_0.2Cu₃Ti₄O₁₂ ceramics sintered at980°C exhibited excellent withstand voltage characteristics with a breakdown voltage of about 24.43 k V/cm.（2）Sr Ti O₃ composite CCTO ceramic material:The dielectric loss（tanδ）of Sr Ti O₃-Ca Cu₃Ti₄O₁₂ ceramic is lower than 0.05 in a wide frequency range（100 Hz-100 k Hz）.In particular,CCTO/0.4STO sintered at 1000°C exhibited a particularly low dielectric loss（only 0.012）at 1 k Hz,and its breakdown voltage was as high as 54.15k V/cm.（3）Zr⁴⁺doped CCTO ceramic materials:The dielectric constant（ε′）and dielectric loss（tanδ）of Ca Cu₃Ti_3.9Zr_0.1O₁₂ ceramics sintered at 1050°C show good stability,and the minimum dielectric loss can be reduced to 0.04 at 10 k Hz.The dielectric constant of the Ca Cu₃Ti_3.9Zr_0.1O₁₂ ceramic samples sintered at 1100°C were all higher than 15000 in the frequency range of 100 Hz-100 k Hz.