Enhanced dielectric response and optical tunability in NH₄I-doped ZrO₂/PVA nanocomposites for advanced electronic applications

NH₄I doped ZrO₂/PVA multifunctional polymer nanocomposite films were successfully fabricated using a simple and cost-effective solution casting method with double distilled water as a solvent. The influence of NH₄I incorporation on the structural, optical, surface morphological, dielectric, and electrical properties of the composite films was systematically investigated. FTIR analysis confirmed the interaction between NH₄I, ZrO₂ nanoparticles, and the PVA polymer matrix, indicating the modification of polymer chain interactions and ionic environments. UV–Visible spectroscopy revealed that NH₄I doping significantly influenced the optical properties by reducing the direct optical band gap from 5.08 eV to 4.95 eV, while the minimum indirect band gap was observed at 4.65 eV. The correlation between optical band gap and refractive indices was evaluated using the Reddy and Singh–Kumar relationships, demonstrating the tunability of optical parameters through ionic doping. Atomic force microscopy analysis confirmed a homogeneous surface morphology with increased surface roughness, indicating effective incorporation of NH₄I within the composite matrix. The dielectric studies revealed higher permittivity at lower frequencies, followed by a gradual decrease with increasing frequency due to Maxwell–Wagner interfacial polarization arising from conductor–insulator interactions. The dielectric constant increased with NH₄I addition up to 10 wt% loading, attributed to enhanced dipolar polarization and ionic contribution within the polymer matrix. Furthermore, the AC conductivity exhibited a continuous increase with increasing NH₄I concentration over the entire frequency range, confirming improved charge transport facilitated by mobile ionic species. The obtained results demonstrate that NH₄I incorporation provides an effective strategy for tailoring the optical and dielectric properties of ZrO₂/PVA nanocomposites. These multifunctional polymer nanocomposites show potential for applications in dielectric energy storage systems, optical coatings, and polymer-based electronic and optoelectronic devices.