Investigation on dielectric properties of the polyimide- based composite films with high permittivity

CaCu3Ti4O12(CCTO) and Zr-doped CaCu3Ti3.95Zr0.05O12(CCTZO) particles with a giant dielectric permittivity were used as filler to prepare Polyimide (PI)-based composites, respectively. Dielectric properties of CCTO/PI and CCTZO/PI composite films have been investigated comparatively. It is found that the dielectric properties of two kinds of composite films with low concentration filler loading have independence on frequency and temperature, while the dielectric permittivity of two kinds of composite films increases remarkably with increasing concentration of filler loading(>20%) and temperature. The dielectric permittivity of CCTZO/PI composite film with a 40% filler loading reaches up to 70 at 10 Hz, which is higher than that (43) of CCTO/PI composite film with the same concentration filler loading. It is also found that the dielectric permittivity of CCTZO/PI composite film can reach about 260 at 150 °C when the concentration of CCTZO loading is 40 vol%. The conductive properties of two kinds of composite films increase with increasing frequency, temperature and concentration of filler loading. The study indicates that dielectric and conductive properties are closely related to the polarization between filler and PI matrix and semiconductive network supported by the percolation theory.