CaCu（3-x）FexTi4O（12）（x=0, 0.015, 0.03, 0.045, 0.06） ceramics were synthesized by sol-gel method. The electrical conduction and dielectric measurements show that the doping of a very small amount of Fe（3＋） ions greatly reduces the low-frequency dielectric constants and leakage, and enhances grain resistivity. For the doped samples, the appearance of the strong low-frequency peaks in the spectra of dielectric loss confirms that the doping of Fe（3＋） ions induces the contact-electrode effect on ceramic surface. These great changes of electrical properties may originate from the reduced amount of oxygen vacancies by doping Fe（3＋）
Zhi YangYue ZhangGuang YouKun ZhangRui XiongJing Shi
Ca1-xRbxCu3Ti4O12 （x=0, 0.01, 0.02 and 0.03） ceramics were synthesized by the sol-gel method. Doping Rb＋ reduces dielectric loss, which reaches minimum when x=0.02. By measuring properties of electrical conduction, larger leakage current density and height of grain-boundary Sehottky potential barrier （φB） were found in the doped samples, and φB became maximum when x=0.02. These results are attributed to the increase in the amount of oxygen vacancies and the formation of Cu-rich/Ti-poor grain-boundary layers, and it can be concluded that the dielectric loss in CCTO ceramic can be reduced by manipulating the composition and electrical properties of grain boundary.
