Investigation on a new multiferroic compound KBiFe 2 O 5 : Structural, optical, electrical and magnetic properties

Photoactive Brownmillerite Multiferroic KBiFe2O5 and Its Potential Application in Sunlight-Driven Photocatalysis

“…For example, the space charges cannot follow the reversal of fields at higher frequencies, and then undergo relaxation due to their large effective mass. 15 From the ε vs T curve (Figure 4a), a maximum ε was observed at about 750–760 K, which is close to the reported Curie temperature ( T c = 780 K) of KBFO. 7 The antiferromagnetic transition for K6 in the M vs T plot (Figure 3b) also sets in at about the same temperature.…”

“…In earlier reports, secondary phases have been observed in KBFO samples synthesized at 650 °C by one-step thermal treatment method. 15,26 Bismuth trioxide (Bi 2 O 3 ) is one of the primary precursors in the synthesis of KBFO. Bi 2 O 3 exists in six different phases such as monoclinic (α-Bi 2 O 3 ), body-centered cubic (γ-Bi 2 O 3 ), face-centered cubic (fcc) (δ-Bi 2 O 3 ), tetragonal (β-Bi 2 O 3 ), triclinic (ω-Bi 2 O 3 ), and orthorhombic (ε-Bi 2 O 3 ).…”

“…It is likely that the magnetic ordering in KBFO influences the electron–electron interaction in the compound, which leads to a lower band gap compared to ferroelectric compounds. 15 Magnetism in such compounds could be an additional advantage in applications such as photocatalysis, to retrieve the catalyst after effluent treatment by applying an external magnetic field. Considering the above option, the magnetic properties of KBFO have been investigated in detail.…”

“…11−14 Typically, Fe-based brownmillerite compounds contain FeO 4 tetrahedra leading to the occurrence of lower band gaps unlike Fe-based perovskites, which consist of FeO 6 octahedra only. 15 The lower band gap of Fe-based brownmillerite compounds is attributed to the presence of shorter Fe–O bond lengths and high covalence in FeO 4 tetrahedron compared to FeO 6 octahedron. 16,17 Oxygen deficiency in the brownmillerite structure also leads to high Curie temperature ( T c ) and lower band gap ( E g ), which is a major advantage over typical ABO 3 perovskite structures.…”

“…4,12,20 In the present work, we explore the synthesis of KBFO by multistep thermal treatment unlike one-step thermal treatment reported by Zhai et al 26 Multistep thermal treatment synthesis can reduce the synthesis temperature to 650 °C compared to previous reports. 15,26…”