Dielectric study and AC conduction mechanism of gamma irradiated nano‑composite of polyvinyl alcohol matrix with Cd0.9Mn0.1S

Abstract

Nanocomposite of PVA and Cd0.9Mn0.1S was prepared by solution casting technique. The formed nanocomposite was irradiated by γ-ray with dosage ranging from 10 to 120 kGy. The dielectric properties of PVA/Cd0.9Mn0.1S nanocomposites were studied as a function of frequency (100 Hz–5 MHz) in a temperature range of (303–413 K). The data were analyzed in the dielectric loss (ε″), electric modulus (M″) and conductivity representation (σ′). Contributions from the polymer matrix and reinforcing phase are discerned in the relaxation response. The α-relaxation and a strong frequency dispersion are identified in the ε″ spectra at high temperatures, which are attributed to the segmental motion of the polymer main chain and to conductivity contribution and /or interfacial polarization, respectively. However, two peaks are detected in the M″ spectra: a main α-relaxation at high frequency and ρ-relaxation relating to the conduction process at low frequency. The temperature dependence of both the ρ-relaxation time obtained from the modulus and dc conductivity (σdc) obeys the Arrhenius law with almost similar activation energies, ≈ 0.67 eV. The change of the frequency exponent, s, with temperature reveals that the ac conductivity is governed by the correlated barrier hopping (CBH) mechanism. The dielectric constant (ε′) and dielectric loss (ε″) are dose dependent showing highest value for 30 kGy irradiated sample in the α-dipolar relaxation region. With increasing γ dose, the ac conductivity increases whereas the binding energy of the charge carriers Wm decreases supporting the dominance of the chain scission in polymer.