Preparation of polyimide/Al2O3 composite films as improved solid dielectrics

Considerable demand for solid thin-film dielectrics with high dielectric constants for use in the fabrication of capacitors has been observed. In this study, polyimide (PI)/Al2O3 composite films were prepared by incorporating different micron-sized α-Al2O3 contents into PI derived from pyromellitic dianyhydride and 4,4′-oxydianiline via ultrasonication. Chemical structure, morphology, dielectric and thermal properties were investigated by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), LCR meter and Perkin Elmer Pyris 6. FTIR spectra showed complete imidization, and all characteristic peaks of the imide groups are observed in PI and PI/Al2O3 composite films. XRD patterns revealed that the PI/Al2O3 composite exhibits peaks similar to those of α-Al2O3, indicating that the crystal structure of α-Al2O3 remains unchanged and stable after being doped into the PI matrix. SEM micrographs showed uniform distribution of α-Al2O3 particles in the PI matrix. Meanwhile, the dielectric constant, dielectric loss and thermal stability of PI/Al2O3 increases with the addition of α-Al2O3 content.