Structure, ferroelectric, magnetic, and energy storage performances of lead-free Bi4Ti2.75(FeNb)0.125O12 Aurivillius ceramic by doping Fe3+ ions extracted from Padang beach sand

Abstract

This work successfully synthesized single-phase Aurivillius Bi4Ti2.75(FeNb)0.125O12 using a molten salt method and the natural precursor of Fe3+ ions extracted from Padang Beach sand. The study extensively examined the phase formation, crystal structure, grain morphology, and physical properties. X-ray diffraction (XRD) analysis combined with the Rietveld refinement technique confirms that Bi4Ti2.75(FeNb)0.125O12 adopts a B2cb orthorhombic structure. The refined atomic positions reveal that Bi3+ ions are located in the A-site within both the bismuth and perovskite layers, while the B-sites within the perovskite layers are primarily occupied by Ti4+/Nb5+/Fe3+ ions. The lower distortion of the inner B(1)O6 octahedra suggests the preference for Fe3+ local clusters. The magnetization hysteresis suggests that the Bi4Ti2.75(FeNb)0.125O12 phase exhibits a weak antiferromagnetic state arising from the local short-range Fe–O–Fe antiferromagnetic ordering in the inner B(1)O6 octahedra. The electrical measurements reveal that the existence of ferroelectric ordering at room temperature comes from the structural distortion and the off-center ionic displacement. The energy storage capacity of 10.15 mJ/cm3 and efficiency (η) of 50.2% were obtained in ceramic sample under an electric field of 70 kV/cm at room temperature.