Study Of Property Improvement Of CaCu₃Ti_4-xNb_xO₁₂Dielectric Ceramics By Doping

CaCu₃Ti₄O₁₂（CCTO）ceramics have been widely studied due to their giant dielectric constant,excellent temperature stability and good frequency stability.With the miniaturization and high density of electronic industry becoming the main trend,the research progress of CCTO dielectric ceramics is getting faster and faster.However,the high dielectric loss of CCTO is still a key problem.In order to further improve the dielectric performance of CCTO,it is necessary to carry out in-depth work to realize its practical application.In this thesis,the CCTO dielectric ceramics were prepared by using solid-state reaction method.A series of doping experiments have been conducted to improve the performance of its dielectric properties.The effects of doping on the microstructures and dielectric properties of CCTO dielectric ceramics were investigated systematically.The main research results of this work are as follows:（1）When Ti is partly doped with a certain amount of Nb(CaCu₃Ti_（4-x）Nb_xO₁₂),the dielectric constant of the CCTO ceramics was significantly improved.The dielectric constant was the highest when Nb doping concentration at 0.05.The highest dielectric constant was about 384000 and the lowest dielectric loss was about 0.189.When doping concentration was more than 0.1,the dielectric constant of the CCTO ceramics began to decline and their dielectric loss increased.（2）On the basis of the CCTNO ceramics with high dielectric constant and high dielectric loss,Nb-Al co-doping(CaCu₃Ti_（4-x-y）Nb_xAl_yO₁₂)was attempted.Doping Al in CCTO can effectively reduce dielectric loss.The doped concentration of Nb was0.05 and the doped concentration of Al was in the range of 0⁰.2.It was found that Nb-Al co-doping can effectively reduce the dielectric loss,but correspondingly their dielectric constant decreases significantly.（3）By reducing the doping concentration of Nb to 0.02 and adding Si O₂ as the second phase in the CCTNO ceramics,the dielectric loss of the CCTNO ceramics was reduced.However,their dielectric constant was also reduced.The CCTNO sample with Nb doping concentration at 0.02 and SiO₂ addition at 0.1 wt%had a dielectric constant twice as much as that of CCTO ceramics,and its dielectric loss was about 0.151,which is better than the CCTNO ceramics without SiO₂.（4）In order to maintain high dielectric constant and low dielectric loss for the CCTNO ceramics,Nb-Mg co-doping(CaCu_（3-x）Mg_xTi_（4-y）Nb_yO₁₂,CCMTNO)was employed.It was found that the CCMTNO ceramics exhibited both high dielectric constant and low dielectric loss.The dielectric constant of CCMTNO ceramics with Nb doping concentration at 0.02 and Mg doping concentration at 0.05 was increased in the frequency range 10³¹0⁵Hz,and their dielectric loss was notably lowered.