Effect of the biphase TiO2 nanoparticles on the dielectric and polaronic transport properties of PVA nanocomposite: Structure analysis and conduction mechanism

Abstract

Polymeric composite films with tunable electrical and dielectric performance have several uses in electronics based on organic materials. This paper reports the fabrication and the role of TiO2 NPS (nanoparticles) on the dielectric and nanocomposites' conduction of pristine polyvinyl alcohol (PVA). The nanopowder of biphase TiO2 and the nanocomposites of different NPS weight percentages have been fabricated via the sol-gel and casting methods. Structure of the synthesized NPS and nanocomposites were analyzed via PXRD (Powder X-ray diffraction), HR-TEM (High-resolution microscopy of transmission electron), and FTIR (Fourier transform-IR). The average size of the biphase TiO2NPS crystallite is around 52 nm, as calculated from Scherer law. Frequency and temperature dependence of dielectric properties have been studied in a wide range. The dielectric constant of the host matrix has been enhanced by adding TiO2NPS. AC conductivity increases with the further addition of TiO2NPS contents, and its frequency dependence follows the universal power law. The nanocomposite with 6.6 wt% of TiO2NPS shows higher conductivity as compared to other concentrations. The exponent power (s) has values in the range of 0.2–0.9, indicating that the conduction mechanism is correlated with barrier hopping (CBH). The dependence of the DC conductivity on absolute temperature has been studied and obeys Arrhenius relation. Three discrete sections were recognized from the AC conductivity spectra. In light of polaronic hopping conduction models, the electrical conductivity data were analyzed. The analysis shows that the high-temperature conductivity is well explained by the polaronic model, while at an intermediate temperature, the Greaves VRH (variable-range hopping) model is appropriate. Also, the non-adiabatic conduction was established in the nanocomposite system via the application of different suggestions. The values of the decay constant and the density of states confirmed the presence of the localized states. Finally, a small polaron coupling constant (γp) is more significant than four, which indicates a strong electron-phonon interaction.