• Murshed, Mohammad Mangir
• Gaczynski, Piotr
• Gesing, Thorsten M.
• Kirsch, Andrea
• Becker, Klaus-Dieter

Abstract

<jats:title>Abstract</jats:title><jats:p>Bi<jats:sub>2</jats:sub>Fe<jats:sub>4</jats:sub>O<jats:sub>9</jats:sub>was synthesized using a polyol-mediated method. X-ray powder diffraction (XRPD) revealed that the as-synthesized sample is nano-crystalline. During heating, the X-ray amorphous powder transformed into a rhombohedral perovskite-type bismuth ferrate followed by a second transformation into mullite-type Bi<jats:sub>2</jats:sub>Fe<jats:sub>4</jats:sub>O<jats:sub>9</jats:sub>at higher temperatures. This transformation was studied at<jats:italic>in-situ</jats:italic>conditions by temperature-dependent XRPD and<jats:sup>57</jats:sup>Fe Mössbauer spectroscopy. The<jats:sup>57</jats:sup>Fe Mössbauer spectra indicate the existence of two Fe<jats:sup>3+</jats:sup>species at two different octahedrally coordinated sites leading to the conclusion that the as-synthesized powder of the polyol synthesis possesses a disordered (Bi<jats:sub>1–<jats:italic>x</jats:italic></jats:sub>Fe<jats:sub><jats:italic>x</jats:italic></jats:sub>)FeO<jats:sub>3</jats:sub>perovskite structure. Rietveld refinements have unambiguously supported this observation and this results suggest that one third of the Bi<jats:sup>3+</jats:sup>sites are substituted by Fe<jats:sup>3+</jats:sup>representing the initial chemical composition. This study has shown that as-synthesized nano-materials are not always similar to the respective micro-crystalline ones.</jats:p>

Topics

• perovskite
• impedance spectroscopy
• amorphous
• chemical composition
• Mössbauer spectroscopy
• Bismuth
• mullite