Effect of Al doping on the electric and dielectric properties of CaCu3Ti4O12

Al-doped CaCu3Ti4-xAlxO12-x/2 (CCTO, x=0-0.1) ceramics were prepared by the solid-state reaction, and their electric and dielectric properties were investigated. Al doping has been shown to reduce the dielectric loss remarkably while maintaining a high dielectric constant. At x=0.06, the loss tangent (tan delta) was below 0.06 over the frequency range of 10(2)-10(4) Hz, and the dielectric constant was 41 000 at 10 kHz. Impedance spectra indicated that Al doping increased the resistivity of the grain boundary by an order of magnitude. The improvement of the dielectric loss in Al-doped CCTO was attributed to the enhanced grain boundary resistivity.