Dielectric measurements in large frequency and temperature ranges of an aromatic polymer

The characterization of the BPDA/PDA polyimide (PI) at high temperature up to 400 °C, thanks to dielectric relaxation spectroscopy (DRS) in the 10-1 Hz to 106 Hz frequency range, allows the determination of the dc electrical conductivity (σdc). In such a high temperature range, the dielectric spectra are modified by the extrinsic electrode polarization phenomenon (EP) response. A model is proposed which coupled to the DRS results allows evidencing and quantifying the effect of the EP. The proposed method gives a simple way to determine the intrinsic σdc values from the effective ac dielectric response, improving the accuracy and reducing the duration of measurement. For BPDA/PDA PI, the resulting σdc values range from 4 × 10-11 to 8 × 10-6 Ω-1 m-1 for temperatures between 200 and 400 °C, with an activation energy of the conduction phenomenon of 0.55 eV.