Synthesis, characterization, and effect of doping on the optical and electrical properties of layered ferroelectric ceramics

Abstract

Aurivillius phases are layered perovskite-type oxides described by the general formula An-1Bi2Bi2O3n+3 where A corresponds to a large cation in 12-fold coordination, while B corresponds to a smaller cation in octahedral (6-fold) coordination. In this study, praseodymium (Pr)-doped SrBi2Nb2O9 ( x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) ceramics were synthesized via a conventional solid-state reaction using carbonate, oxide, and nitrate precursors dissolved in a citric acid–ethylene glycol solution. X-ray diffraction analysis confirmed that the samples crystallized in the orthorhombic structure typical of SrBi₂Nb₂O₉, with a gradual decrease in unit cell volume upon Pr incorporation. FTIR spectroscopy revealed vibrations associated with the NbO₆ octahedra, while photoluminescence measurements confirmed the presence of Pr³⁺ ions. UV-Vis spectroscopy indicated a direct band gap whose value depends on the doping level. The Curie temperature, which remained constant across different frequencies, confirmed the normal ferroelectric behavior of the ceramics. The ferroelectric transition was found to be more sensitive to the Pr substitution site than to its valence, showing no linear correlation with Pr³⁺ concentration. At room temperature, Pr doping did not significantly affect dielectric loss, whereas at elevated temperatures, electrical conduction was dominated by doubly ionized oxygen vacancies and a hopping mechanism.