Effect of 90 MeV oxygen and carbon ion irradiation on structural, optical and dielectric properties of ZnO embedded in PVA matrix

Abstract ZnO nanoparticles embedded in polyvinyl alcohol (PVA) matrix have been synthesized by solution casting method. The samples were irradiated with 90 MeV O 7+ and C 6+ ions to different fluences. The structural characterization indicated the semicrystalline nature of PVA along with the formation of ZnO/PVA nanocomposite. The reduction in the peak intensity of the sample upon ion irradiation is due to the chain scissions as well as creation of free-radicals. The crystallite size of the sample increased from ∼5.57 to 6.47 nm with increasing fluence. The morphological study reveals the uniform distribution of the ZnO nanoparticles inside the PVA matrix upon ion irradiation. UV–visible absorption study indicated the presence of both direct and indirect band gap transitions in the sample. Although, the direct band gap of the sample decreased slightly at the initial ion fluence, but the same increased from ∼2.95 to 3.82 eV and ∼2.95 to 3.73 eV with increasing ion fluence from 0 to 1 × 10 12 ion cm −2 , for 90 MeV O 7+ and C 6+ ion irradiation, respectively. Similar features have also evidenced for the indirect band gap transition. This could possibly be due to the chain scission or cross linking of polymer. The reduction in both real part and imaginary part of impedance with the progress of frequency along with the shifting of impedance peak upon ion irradiation demonstrates the presence of a relaxation process in ZnO/PVA nanocomposite. Both the ion irradiation led to the alteration in dielectric constant and loss, electric modulus, impedance and AC electrical conductivity of the sample. The increase of electrical conductivity of the ZnO/PVA nanocomposite at certain ion fluences of irradiation could be due to uniform dispersion of ZnO inside the PVA matrix as well as the increase of free radicals, unsaturation, loss volatile fragments, etc due to breaking of chemical bonds.