Ferroelectric and photoelectrochemical studies of lead-free Ba0.925Bi0.05 □0.025(Ti0.65Zr0.30Sn0.05)O3 ceramic and its application to Rhodamine B oxidation under solar light

Abstract

New materials with general formula Ba0.925Bi0.05□0.025(Ti0.65Zr0.30Sn0.05)O3 (symbolized BBiTZS) were prepared by high-temperature solid-state reaction. The room X-ray diffraction pattern suggests a cubic perovskite structure. The thermal variation of the permittivity at different frequencies showed a relaxor ferroelectric behavior. The Raman spectroscopy was in accordance of the dielectric measurements. The diffuse phase transition parameters were determined from the modified Curie–Weiss law, while the relaxor behavior was highlighted by a good fit to the Vogel–Filcher relationship. The capacitance-potential (Csc−2 − E) graph at pH ∼ 7 is characteristic of n-type behavior with a flat band potential (Efb) of −0.52 VSCE and an electron density (NA) of 2.7 × 1018 cm−3. The Electrochemical Impedance Spectroscopy, measured in the region (1 mHz - 105 Hz), showed a semicircle, assigned with the bulk property (27 kΩ cm2); a constant phase element (CPE) is responsible for the depletion angle (−9°). With an optical of 2.00 eV, the ferroelectric BBiTZS possesses appealing photocatalytic capability and was successfully experimented for the oxidation of Rhodamine B (Rh B) exposed to solar light. According to the band diagram, electrons from the conduction band of BBiTZS are injected into dissolved oxygen, resulting in O2· radicals, which are employed in the Rh B oxidation. UV–Visible spectrophotometry was used to follow the Rh B discoloration. On a solar irradiation of 97 mW cm−2, a conversion of 50% is achieved in Rh B solution (10 mg L−1) within 100 min., and the degradation follows a first order kinetic model with a half photocatalytic-life of 90 min.

Keywords

• Lead-free perovskite
• Relaxor behavior
• Dielectric properties
• Photocatalysis
• Solar light