The CaCu3Ti4-xAlxO12-x/2(CCTAO) (x=0, 0.06, 0.10, 0.20) ceramics is prepared by the solid-state reaction. The effect of Al on the dielectric properties and microstructure revolution of CCTAO ceramics are studied. The results indicate that Al-doping improve the growth of small grain and prevent that of the large grain at grain boundary. Meanwhile, the increase of insulating performance of grain boundary lead to the dielectric relaxation properties at lower frequency obviously weakened and the dielectric loss at lower frequency decreased. At x=0.2, the tan δ is less than 0.05 in the frequency range of 40 Hz～1 kHz and the minimum 0.033 at 140 Hz. The dielectric properties under direct current(DC) bias shows that the substitution of Al3+ for Ti4+ realized the P-type doping and changed the semi-conduction condition of substrate and their interface, which weakened the performance of permittivity and dielectric loss under DC bias voltage.

giant dielectric constant; dielectric relaxation; direct current(DC) bias voltage