Study Of Preparation And Dielectric Properties Of Al And Zr Doped CaCu₃Ti₄O₁₂ Ceramics

CaCu₃Ti₄O₁₂（CCTO）is an important perovskite-like ceramic dielectric material.As the main material of capacitors and the dielectric layer of microelectronic devices,it has a wide range of application prospects in the field of electronics.CCTO ceramics have the advantages of simple preparation,environmental protection,stable performance and high dielectric constant.However,its application is limited by its high dielectric loss,poor frequency stability and sensitivity to the preparation process.In this research,Al and Zr are mainly used for doping modification of CCTO ceramics,in order to optimize the comprehensive dielectric properties of CCTO.The main research is as follows:（1）Ca Cu_3-xAl_xTi₄O₁₂（x=0.00,0.02,0.04,0.06,0.08,）was prepared by doping Al at CCTO copper site by solid phase reaction method.The results show that the lattice constant of CCTO decreases and the crystal structure does not change with Al³⁺successfully replacing Cu²⁺.In addition,Al doping can inhibit the abnormal growth of grain,reduce the average grain size of ceramic samples,and improve the size uniformity of grain significantly.Compared with undoped CCTO,the dielectric constant of Al-doped ceramics is significantly improved in the frequency range of 10²-10⁶ Hz,and the best effect is achieved when the Al doping amount x=0.06.At room temperature Ca Cu_2.94Al_0.06Ti_3.96Zr_0.04O₁₂ ceramic dielectric constant of 3338（1 k Hz）,dielectric loss is 0.0402（1 k Hz）,excellent dielectric properties frequency stability.Further analysis shows that Al doping reduces the grain resistance,enhances the semiconducting of the grain,and finally significantly increases the dielectric constant of the sample,while the decrease of grain boundary resistance is the reason for the increase of dielectric loss of the ceramic sample.（2）Ca Cu_3-xAl_xTi_4-yZr_yO₁₂（x=0.06,y=0.00,0.02,0.04,0.06,0.08）was prepared by co-doping Al and Zr with CCTO ceramics by solid phase reaction method.XRD shows that the crystal structure of CCTO is not changed by Al and Zr co-doping,and the lattice constant of CCTO increases when Zr⁴⁺replaces Ti⁴⁺.The microstructure shows that appropriate Zr addition can further refine grain and improve grain uniformity on the basis of Al addition.The addition of Zr significantly reduces the dielectric loss of CCTO and improves the frequency stability of CCTO dielectric properties.The performance is optimal when the doping amount of Zr is y=0.06.At room temperature Ca Cu_2.94Al_0.06Ti_3.96Zr_0.04O₁₂ ceramic dielectric constant of 3338（1k Hz）,dielectric loss is 0.0402（1 k Hz）,excellent dielectric properties frequency stability.Impedance analysis shows that Zr significantly increases the grain boundary resistance,which not only reduces the dielectric loss of ceramic samples,but also enhances the dielectric property frequency stability of ceramic samples.（3）Solid instead should method is used to explore the sintering temperature on Ca Cu_2.94Al_0.06Ti_3.96Zr_0.04O₁₂ ceramic dielectric properties.Ceramic samples were successfully prepared by sintering at 1000℃,1020℃,1050℃,1080℃and 1100℃,while the samples were fused at 1150℃.XRD shows that the samples prepared successfully are all CCTO,but the titanium dioxide heterodox peaks appear in the samples sintered at 1100℃.The grains and grain boundaries of the samples sintered at 1000℃and 1020℃are not obvious,and the dielectric properties are poor.The samples sintered at 1050℃and 1080℃have obvious grain and grain boundary and excellent dielectric properties.The lowest dielectric loss of samples sintered at 1050℃is 0.0402（room temperature,1 k Hz）,and the highest dielectric constant of samples sintered at 1080℃is 5900（room temperature,1 k Hz）.The sample sintered at 1100℃showed over-burning phenomenon,and the dielectric properties began to decline.Studies have shown that Ca Cu_2.94Al_0.06Ti_3.96Zr_0.04O₁₂ ceramic sintering temperature between 1050℃to 1080℃is more appropriate.