Effect of 90 MeV O7+ ion irradiation on the properties of ZnO/PVA nanocomposite: a ZnO concentration dependence study

The present study examines the influence of 90 MeV O⁷⁺ ion irradiation on ZnO/PVA polymeric nanocomposites with varying ZnO nanoparticle concentrations (1.5 mg and 5 mg). The crystallite size of PVA nanocomposite with low and high ZnO content decrease from ~ 6.8 to 5.3 nm and ~ 7.6 to 6.9 nm, respectively, with increasing fluence from 0 to 1 × 10¹² ions cm⁻². Reduction of crystallite size with increasing fluence is more pronounced in the low ZnO content as compared to high ZnO content, signifying the enhancement of radiation hardness of high ZnO content systems. Morphological features indicated that ion irradiation facilitates the dispersion of filler particles inside the PVA matrix. The decrease of optical band gap with the increasing ion fluence attributed to the creation of carbonaceous clusters along the energetic latent ion tracks due to irradiation-induced chain scission, cross-linking, free radical formation, etc. The maximum value of dielectric constant is observed for sample with low ZnO content when irradiated at a fluence of 5 × 10¹⁰ and 5 × 10¹¹ ions cm⁻² whereas the same is observed for sample with the highest ZnO content irradiated at the fluence of 5 × 10¹¹ ions cm⁻². The space charge polarization or dipolar relaxation could contribute to the reduction in dielectric loss in the low-frequency regime. The upsurge in dielectric loss with increasing ion fluence may be ascribed to the interfacial polarization in such heterogeneous system or due to the improvement in the segmental motion of polymeric chains. The AC conductivity of the sample with low ZnO content improved upon ion irradiation while the same for the sample with the highest ZnO content decreased except at the fluence of 5 × 10¹¹ ions cm⁻². The improvements in dielectric properties are indicative of a good interaction between ZnO nanoparticle  and the PVA matrix. The modification in the properties of ZnO/PVA nanocomposite upon ion irradiation could be attributed to the formation of free radicals, breaking of covalent bonds, chain scission, and polymer chain cross-linking. These results show that swift heavy ion irradiation effectively tailors the properties of ZnO/PVA nanocomposites, offering potential for advanced electronic and optoelectronic applications.