AC electrical and optical characterization of epoxy-Al2O3 composites

The AC electrical and optical characterizations of epoxy-alumina (Al2O3) composites have been investigated. Sheets filled with alumina were prepared with different alumina concentrations (0, 2, 5, 8, 10, and 15 wt%). The AC electrical properties were measured by using impedance spectroscopy as a function of applied frequency in range from 50 kHz to 1 MHz and filler concentration. The results obtained showed that the applied frequency and filler concentration was found to influence the AC electrical conductivity and dielectric behavior of the prepared composites. The UV-optical results obtained were analyzed in terms of the absorption formula for non-crystalline materials. The absorption coefficient and the optical energy gap (E-opt) have been obtained from the direct allowed transitions in k-space at room temperature. The tail widths (Delta E) of the localized states in the band gap were evaluated using the Urbach-edges formula. It was found that both (E-opt) and (Delta E) vary with the alumina concentration dispersed in the epoxy matrix. The refractive index (n) for the composites was determined from the collected transmittance and reflectance spectra. The dispersion behavior of the refractive index is discussed in terms of the single oscillator model.