Analysis of electrical microstructure and sensor response in cerium oxide fibers-based interdigitated electrode (IDE) devices

Abstract

Cerium oxide fibers were synthesized using an electrospinning technique with an optimum PVP to Ce (CH₃COO)₂ ratio of 1:1. Scanning electron microscope images of CeO₂ sample calcined at 600 °C revealed highly porous and uniform fibers with an average diameter of ~ 92 nm. X-ray diffraction analysis confirmed the formation of small crystallite size, single-phase polycrystalline CeO₂ fibers. Thermo-gravimetric and differential thermal analyses of PVP/Ce-acetate composite fibers indicated complete decomposition of PVP and all volatile components below 600 °C, as confirmed by FTIR analysis. UV–Visible spectroscopy revealed a wide direct band gap of ~ 3.11 eV. The cerium oxide fibers electrical microstructure confirmed via temperature-dependent impedance studies revealed a metallic behaviour in the temperature ranging from 30–170 °C C which is attributed to the existence of high concentration of Ce⁺³ cations due to oxygen vacancies. The activation energies associated with grains and grain boundaries are 0.02267 eV and 0.025 eV, respectively. Above 170 °C, CeO₂ fibers exhibit semiconductor behaviour which is attributed to the dominance of Ce⁴⁺ cations and the associated activation energies for the grains and grain boundaries are 0.1104 eV and 0.1181 eV, respectively. The analysis of the CeO₂ fibers-based humidity sensor revealed its potential application due to the effectively polarization of the carriers at low frequencies and suggested a protonic conduction model via Grotthuss mechanism.