Investigation of structural, optical, dielectric properties, and electrical conductivity mechanism of Sr2CeO4: Experimental and DFT studies

Abstract

Sr2CeO4 Ruddlesden–Popper oxide, was synthesized via the solution combustion method and characterized using TGA-DSC, FTIR, and XRD. XRD analysis revealed an orthorhombic structure with space group Pbam, and Rietveld refinement provided accurate lattice parameters, validated by DFT calculations. UV–visible spectroscopy revealed an indirect band gap of 2.23 eV. The electrical and dielectric properties were analyzed from 300 to 600 °C and 20 Hz to 2 MHz. AC conductivity follows Jonscher's power law, and the Overlapping Large Polaron Tunneling (OLPT) model to AC conductivity mechanism. Key parameters such as Rω, N(EF), and WHO were obtained by fitting the OLPT model to the conductivity data. The activation energy for DC conduction was determined to be 0.89 eV, ascribed to the hopping of doubly ionized oxygen vacancies (VO¨). The high dielectric constant value at low frequencies indicated a significant contribution to interfacial polarization. Impedance spectroscopy is used to separate the contribution of grain and grain boundary to the total conductivity. A similar value of activation for total conductivity and grain resistance supported conduction through grains. © 2025