Electrical, thermal, optical, and magnetic properties of ZTO nanocomposites in a PVA matrix: functional correlations with non-thermal structural modifications

ZTO/PVA nanocomposite sheets were successfully fabricated using precipitation and sonochemical routes for ZnO and TiO 2 nanoparticle synthesis, respectively, followed by solution casting into the PVA matrix. This process ensured uniform dispersion of ZTO nanoparticles within the polymer matrix and was completed without post-mixing thermal calcination, representing an energy-efficient and novel synthesis route. XRD analysis confirmed the incorporation of nanoparticles and revealed an anatase-to-rutile phase transformation of TiO 2 after composite formation. XPS spectra confirmed the presence of Zn, O, and Ti LMM signals, indicating the presence of oxide components within the composite structure. Optical analysis showed a significant reduction in the band gap after ZTO incorporation. The indirect band gap decreased from 3.03 eV for pure PVA to 2.93, 2.72, and 2.5 eV for 2, 5, and 8 wt% ZTO/PVA, respectively, while the direct band gap decreased from 4.59 to 2.72 eV at higher filler loading. Photoluminescence results showed a slight red shift for 2 and 5 wt% ZTO/PVA due to interfacial defect states, followed by a blue shift at 8 wt% associated with near-band-edge emission and phase transformation effects. AFM analysis revealed a significant increase in surface roughness from 9.46 to 131.97 nm as ZTO content increased, indicating nanoparticle aggregation and surface heterogeneity. Thermal analysis demonstrated improved thermal stability and multi-step degradation behaviour. Dielectric measurements showed high permittivity at low frequencies due to interfacial polarisation, with non-Debye relaxation behaviour confirmed by Havriliak–Negami and Cole–Cole analysis. Magnetic measurements indicated predominantly non-magnetic behaviour with a slight enhancement after ZTO incorporation. These findings demonstrate that the addition of ZTO effectively tailors the structural, optical, thermal, dielectric, and magnetic properties of PVA nanocomposites, making them promising for multifunctional dielectric and optoelectronic applications.