Reinspection of low temperature synthesis of bulk Bi3Fe5O12 (BIG): An aqueous sol-gel processing

In this study for the synthesis of bismuth iron garnet (Bi3Fe5O12; BIG) powders an aqueous sol-gel processing route has been used. Due to the metastability the Bi3Fe5O12 was mostly prepared in thin films form. Only few studies demonstrated the possibility to prepare bulk single-phase BIG. In the suggested sol-gel processing the bismuth nitrate pentahydrate Bi(NO3)3·5H2O and iron nitrate nonahydrate Fe(NO3)3·9H2O, were used as Bi and Fe starting materials, respectively. The 1,2-ethanediol (EG) and citric acid (CA) were selected as complexing agents to ensure the homogeneity of resulted Bi–Fe–O gels. The synthesis products were characterized by X-ray powder diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and Mössbauer spectroscopy. The obtained results clearly showed that the perovskite BiFeO3 (BIP) crystalline phase instead of garnet has formed confirming the ambiguity of previously published results on the synthesis and characterization of bulk Bi3Fe5O12. SEM micrographs of bismuth ferrite sample synthesized at 500 °C using citric acid as complexing agent in the sol-gel processing. [Display omitted] •Sol-gel method was applied for the preparation of bismuth iron garnet Bi3Fe5O12 powders.•The perovskite BiFeO3 phase instead of garnet has formed at 500 °C.•The hyperfine parameters of Mössbauer spectrum were consistent with BiFeO3.•The results confirmed the nonthermodynamical character of the garnet Bi3Fe5O12 phase.•The ambiguity of previously published results on the synthesis of bulk Bi3Fe5O12 is discussed.