International audienceDielectric properties of CaCu3Ti4O12 (CCTO)-based ceramics and thick films (e ∼50m) 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 (εr ∼1.4×105) and relatively small dielectric losses (tan δ ∼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 (εr ∼5×104). 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

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In power electronics, the development of new IGBT power modules allows them to switch kV and kA during ps .However, such components need to be cooled and ceramic materials like AlN and Al,O,are used as an interface between the electronic devices (the chips) and the cooling. Such materials have to present very well known electrical and thermal characteristics since the reliability of the inverters these components are used in is strongly dependant on them. In order to increase the knowledge of the physical mechanisms involved during aging of these materials, we present in this paper the very first results obtained in this field. Finally, all these results are discussed and analyzed in view of power electronics applications.