Electrical Conductivity, Dielectric Behavior and EMI Shielding Effectiveness of Polyaniline-Yttrium Oxide Composites

Polyaniline-yttrium trioxide (PAni-Y2O3) composites were synthesized by the in-situ polymerization of aniline in the presence of Y2O3. The composite formation and structural changes in these composites were investigated by X-ray diffraction (XRD), Fourier transform infra red spectroscopy (FTIR), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The direct current (DC) electrical conductivity of the order of 0.51 x 10(-2) S cm(-1) - 0.283 S cm(-1) in the temperature range 300 K-473 K indicates semiconducting behavior of the composites. Room temperature AC conductivity and dielectric response of the composites were studied in the frequency range of 10 Hz to 1 MHz. The variation of AC conductivity with frequency obeyed the power law, which decreased with increasing weight percentage (wt %) of Y2O3. Studies on dielectric properties shows the relaxation contribution coupled by electrode polarization effect. The dielectric constant and dielectric loss in these composites depend on the content of Y2O3 with a percolation threshold at 20 wt % of Y2O3 in PAni. Electromagnetic interference shielding effectiveness (EMI SE) of the composites in the frequency range 100 Hz to 2 GHz was in the practically useful range of -12.2 dB to -17.2 dB. The observed electrical and shielding properties were athibuted to the interaction of Y2O3 particles with the PAni molecular chains.