Synthesis and thermodynamic stability of multiferroic BiFeO3

Development of microcontroller based thermogravimetric analyzer

“…11) results and XRD pattern (Fig. 12) results are in good agreement with the results published [6][7][8][9][10].…”

Reaction pathways in the solid state synthesis of multiferroic BiFeO3

“…One of the first works date back to the sixties when Achenbach et al already reported that during the synthesis of stoichiometric BiFeÜ3, the kinetics of phase formation in the BÍ203-Fe2Ü3 system easily results in the appearance of the sillenite-type BÍ25FeÜ39 and the mullite-type BÍ2Fe4Ü9 impurity phases. 7 These secondary by-products have been interpreted as intermediates in the formation of the ferrite, 8 ' 9 but the fact is that their elimination through a simple mixed-oxides solid state reaction route has proven extremely difficult if not impossible. [10][11][12] Many alternative strategies have been (are being) attempted to prepare puré BiFeÜ3, from a rapid liquid-phase sintering, 13 ' 14 a microwave or spark-plasma assisted sintering, 15 ' 16 or even a mechanochemical high energy milling processing, 17 to different wet chemical methods [18][19][20][21][22][23][24] ; but even in those that have succeed, the precise reaction mechanisms have not been identified yet.…”

Synthesis, microstructure and properties of BiFeO₃-based multiferroic materials: A review

“…Actually many works in the specialized literature claim the difficulty in obtaining a pure BiFeO 3 phase and the unfeasibility to avoid the presence of secondary phases [40,[42][43][44][45]. According to the phase diagrams, slight deviations from the stoichiometric composition would result in a mixture of BiFeO 3 and Bi 25 FeO 40 phases if we move to Bi 2 O 3 rich compositions or in a mixture of BiFeO 3 and Bi 2 Fe 4 O 9 if we move to the Fe 2 O 3 rich area, but it would be possible to obtain a pure BiFeO 3 with a careful stoichiometric control.…”

“…On the other hand, some other authors assert that bismuth ferrite is actually a metastable phase [44,45] Again, the conditions at which BiFeO 3 decomposes are source of discussion. For example Morozov et al [40] stated that BiFeO 3 decompose at temperatures higher than 780 ºC.…”

“…For example Morozov et al [40] stated that BiFeO 3 decompose at temperatures higher than 780 ºC. On the contrary, Carvalho et al [44] avowed that BiFeO 3 decomposes at temperatures below 600 ºC, being possible to obtain a pure phase with a fast cooling that avoids its decomposition. In 2009, by means on high temperature X-ray diffraction measurements Selbach et al [45] For example, in consonance with the proposal by Valant et al [43] the presence of impurities with a larger solubitily in the Bi 2 Fe 4 O 9 or Bi 25 FeO 39 secondary phases than in the BiFeO 3 may increase the stability range of these secondary phases shifting the equilibrium of reaction 2 towards the left.…”