Nanostructures of Sr²⁺doped BiFeO₃multifunctional ceramics with tunable photoluminescence and magnetic properties

Abstract

Careful tuning of formation (calcination) temperature of Sr(2+) doped BiFeO(3) multiferroic ceramics results in tailorable particle morphologies ranging from spherical to pillar-like. Based on the minimization of Gibb's free energy approach, the dominant homogeneous mechanism for particle growth is suggested. The chemical substitution of a trivalent ion (Bi(3+)) by a divalent ion (Sr(2+)) causes the transformation of certain fraction of Fe(3+) to Fe(4+) and/or the appearance of oxygen vacancies. This has been respectively proved by the analysis of XPS and refinement of neutron diffraction data. Although significant modification in the particle morphology is observed, the crystal unit cell remains rhombohedral with a R3c space group but interesting variations in physical properties are achieved. O-vacancies induced strong and sharp photoluminescence activity in the IR region, similar to ZnO, is reported for the first time. This observation opens up a new application for multiferroic ceramics. SQUID M-H data confirms the straightening of the canted spin structure of BiFeO(3), which in turn results in magnetism similar to ferromagnetic materials. Findings of the magneto-dielectric effect are also discussed to claim the multiferroic nature of the sample.

Enhanced visible-light activities of porous BiFeO3 by coupling with nanocrystalline TiO2 and mechanism

“…3C shows the PL spectra of P-BFO and T/P-BFO nanocomposites with the excitation wavelength of 325 nm. It is observed that the P-BFO and T/P-BFO nanocomposites exhibit strong PL signals (blue emission) at the wavelength range from 350 to 525 nm, which is mainly attributed to the electronic transitions from the conduction band of BFO to its valance band [30,31]. Generally speaking, lower the PL signal, lower the charge recombination rate and higher the separation efficiency.…”

A-site strontium doping effects on structure, magnetic, and photovoltaic properties of (Bi1−Sr )FeO3− multiferroic ceramics

“…Magnetization hysteresis loops of (Bi 0.95 Sr 0.05 )FeO 3 À δ (BFO5Sr) ceramic show a weak ferromagnetism due to straightening of the Fe-O-Fe bond angle [10]. X-ray photoelectron spectroscopy and neutron diffraction of (Bi 1 À x Sr x )FeO 3 À δ (x¼ 0.0-0.5) ceramics synthesized using a modified gel-combustion, suggest that the Bi 3 þ -Sr 2 þ substitution causes Fe 3 þ -Fe 4 þ transformation and oxygen vacancies [10]. Structures of (Bi 1 À x Sr x )FeO 3 À δ (x¼ 0.0-0.5) remain in the rhombohedral R3c space group and rhombohedral distortion decreases with increasing Sr 2 þ content [10].…”

“…X-ray photoelectron spectroscopy and neutron diffraction of (Bi 1 À x Sr x )FeO 3 À δ (x¼ 0.0-0.5) ceramics synthesized using a modified gel-combustion, suggest that the Bi 3 þ -Sr 2 þ substitution causes Fe 3 þ -Fe 4 þ transformation and oxygen vacancies [10]. Structures of (Bi 1 À x Sr x )FeO 3 À δ (x¼ 0.0-0.5) remain in the rhombohedral R3c space group and rhombohedral distortion decreases with increasing Sr 2 þ content [10]. It was reported that Sr doping can stabilize the BFO perovskite structure [11].…”

“…For instance, spontaneous magnetization of (Bi 1 À x Ba x )FeO 3 À δ ceramics increases with increasing Ba content [6]. Magnetization hysteresis loops of (Bi 0.95 Sr 0.05 )FeO 3 À δ (BFO5Sr) ceramic show a weak ferromagnetism due to straightening of the Fe-O-Fe bond angle [10]. X-ray photoelectron spectroscopy and neutron diffraction of (Bi 1 À x Sr x )FeO 3 À δ (x¼ 0.0-0.5) ceramics synthesized using a modified gel-combustion, suggest that the Bi 3 þ -Sr 2 þ substitution causes Fe 3 þ -Fe 4 þ transformation and oxygen vacancies [10].…”

BiFeO3–CoFe2O4–PbTiO3 composites: structural, multiferroic, and optical characteristics

“…Much attention has been paid toward BFO-based single-phase multiferroic materials due to their potential applications in transducers, sensors, memories, spintronics, and owing to their interesting physics background [3]. Therefore, BFO-based multiferroics have been studied widely in ceramics as well as in thin film-related aspects [4][5][6].…”