Dielectric properties of CaCu3Ti4O12 ceramics doped by La3+

XRD, SEM, EDS and XPS were used to study the influence of La3+ on phase structure, microstructure, cationic distribution and cationic oxidation state of CaCu3Ti4O12 ceramics. It was found that donor doping is formed by preferential substitution of La3+ for Ca2+. The concentration of O in the grain is increased and the segregation of Cu into the grain boundary is suppressed effectively by La3+ doping, leading to the decrease and uniform distribution of gain size. The influence of La3+ on dielectric properties of CaCu3Ti4O12 ceramics were investigated also by Novocontrol broadband dielectric spectrometer. It was found that oxygen vacancy-related dielectric relaxation at medium frequency region is suppressed and the corresponding dielectric loss is significantly reduced also. At the same time, high frequency dielectric relaxation is increased obviously, which results in a significant increase of dielectric constant from about 5 x 10(3) to 2 x 10(4). The study in this paper shows that donor doping is an effective way to modulate intrinsic point defects, microstructure and then dielectric properties of CaCu3Ti4O12 ceramics.