Study the influence of the crystal structure of the co-precipitated brownmillerite CaFeO_2.5+δ sample on optical and magnetic properties

Abstract

In this study, the brownmillerite CaFeO_2.5+δ sample has been prepared by co-precipitation method. The brownmillerite CaFeO_2.5+δ sample crystallizes in a distorted orthorhombic (Pcmn space group) structure as confirmed by Rietveld analysis of the X-ray diffraction (XRD). Structural characterization also of the brownmillerite CaFeO_2.5+δ sample has been carried out by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), and ultra-high resolution transmission electron microscopy (UHR-TEM). Mössbauer spectroscopy revealed that the brownmillerite CaFeO_2.5+δ sample contained Fe³⁺ in both octahedral and tetrahedral sites. Furthermore, there is Fe^3.5+ in the octahedral site because of the excess oxygen content (δ = 0.0185). The UV-Vis. absorption spectrum of the brownmillerite CaFeO_2.5+δ sample exhibits two absorption peaks in the UV range and two broad absorption peaks in the visible range. The hysteresis loop M (H) of the brownmillerite CaFeO_2.5+δ sample indicated the presence of antiferromagnetic ordering with a small amount of weak ferromagnetic. Present results support that the brownmillerite CaFeO_2.5+δ sample is useful for industrial applications.

Keywords:

• Brownmillerite CaFeO_2.5+δ
• coprecipitation method
• structural characterization
• Mössbauer spectroscopy

Acknowledgments

The authors thank the Science, Technology & Innovation Funding Authority (STDF), Egypt, for supporting the work through Advanced Lab for Energy Storage applications (ALESA).

Disclosure Statement

No potential conflict of interest was reported by the authors.