CaCu_Ti_4O_(12) ceramics from co-precipitation method: Dielectric properties of pellets and thick films

摘要

Dielectric properties of CaCu_3Ti_4O_(12) (CCTO)-based ceramics and thick films (e approx 50 mum) prepared from powders synthesized by a soft chemistry method (co-precipitation) are presented and discussed. The characteristics of pellets and thick films are compared. The pellets exhibit high values of the dielectric permittivity (epsilon_r approx 1.4 x 10~5) and relatively small dielectric losses (tan delta approx 0.16) at 1 kHz and room temperature. These properties are independent of the nature of the metallization of the electrodes. In addition, the dielectric permittivity decreases when the diameter of the electrodes of the pellets increases, while the losses remain constant. This result, which is strongly related to the nature of the dielectric material in between the electrodes, constitutes a strong indication that the high dielectric permittivity values observed in this material are not related to an interfacial (electrode material) related mechanism but is an internal barrier layer capacitor (IBLC) type. Very high values of the dielectric permittivity of CCTO thick films are measured (epsilon_r approx 5 x 10~4). The differences in dielectric permittivity between thick films and dense pellets may be attributed to the difference in grain size due to different CuO contents, and to the different reactivity of the materials.