Scaling behavior of AC conductivity and modulus spectra of K2NiO4-type Sr2TiO4

Abstract

The layered perovskite oxide Sr2TiO4 was synthesized via a solid-state reaction route. X-ray diffraction, employing Rietveld refinement, confirmed its single-phase nature and tetragonal crystal structure within the I4/mmm space group. Field-emission scanning electron microscopy showed a compacted microstructure with irregular polygon-shaped grains characterized by distinct edges and facets. At lower frequencies, the higher dielectric constant indicates interfacial polarization, while the elevated dissipation factor is attributed to DC conduction. The AC conductivity spectra of the sample follow the universal Jonscher’s power law. The same activation energy for relaxation and conduction suggested that both mechanisms are driven by the migration of doubly ionized oxygen vacancies. The presence of oxygen vacancies is further confirmed by X-ray photoelectron spectroscopy. The scaling behaviors in the electrical conductivity and modulus spectra suggest a conduction mechanism independent of temperature. The impedance spectroscopy analysis revealed dominating nature of the grain boundaries in electrical conduction. Combined impedance and modulus plots indicate a transition in charge carrier domain from short-range to long-range migration with increasing temperature. The sample shows potential for next-generation medium-permittivity radio wave dielectric ceramics, attributed to its distinctive characteristics. © Qatar University and Springer Nature Switzerland AG 2024.