Polyimide/BaTiO3 composites with controllable dielectric properties

The polyimide/barium titanate (BaTiO3) composites were successfully synthesized through a colloidal process. In this process, the preparing suspension of fine BaTiO3 particles in poly(amic acid) solution, the film casting of the suspension, and the imidization with heat treatment are involved in sequence. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM), thermal-gravimetric analyses (TGA) and electrometer were used to characterize the structure and properties of the obtained composites. It was found that the BaTiO3 particles in the size of 100 nm were dispersed homogeneously in the polyimide matrix without aggregation. Thermal stability of the composites could be improved with the incorporation of BaTiO3. The dielectric constant (ε) and the dielectric loss (tan δ) of these composites increased with the increase of the volume fraction of BaTiO3 particles. ε, tan δ was 35 and 0.0082, respectively at 10 kHz as the composite contains 50 vol% BaTiO3. Also, the dielectric properties of the composites displayed good stability within a wide range of temperature or frequency.