The phase transition and phase stability of magnetoelectric BiFeO3

A study of phase stability of BiFeO3 has been carried out employing a solid-state ionic titration technique, which involved yttria-stabilized zirconia (YSZ) solid electrolyte. As oxygen was intermittently titrated out of the sample, the oxygen activity monotonically decreased in the system until the oxygen nonstoichiometry in the BiFeO3 phase reached its limiting value. We have observed the appearance of a plateau at this point where the BiFeO3 phase started to undergo a decomposition reaction. X-ray diffraction data show that BiFeO3 phase is transforming to a new Bi25FeO40 phase. Especially, an interesting result is that Bi2Fe4O9 was determined in the decomposed components. Therefore, further research is needed about the decomposition reaction of BiFeO3. This work is useful for the production of novel devices.