Air-gap capacitance cell for the investigation of porous or solvent containing dielectric films

An air-gap capacitance cell is presented, designed for temperature dependent dielectric spectroscopy on materials that cannot be contacted with surface electrodes: materials such as porous foams and membranes or solvent containing polymer resins. The capability of the system is demonstrated with measurements up to 300 °C, performed on a 60 μm porous poly(tetrafluoroethylene) (PTFE) and on a precured hybrid system of a porous PTFE, soaked with the low-k aromatic ether polymer: poly(1,1,1-triphenyl ethane perfluorocyclobutylether). The measurement system allows recording of the dielectric loss spectra with high resolution, barely influenced by thermal expansion or ionic conductivity.