Structural, microstructural and dielectric properties of nanostructured mechanically alloyed polycrystalline Bismuth Ferrite (BiFeO₃)

This paper reports the synthesis and characterization of polycrystalline Bismuth Ferrite (BiFeO₃) by high energy ball milling method (HEBM). Bismuth ferrite was mechanically alloyed in a hardened steel vial for 6 h and subsequent molding; the pellet samples went through multi-sample sintering, where the samples were sintered from 425 to 775 °C with 50 °C increments. The phase characterization by X-ray diffraction (XRD) revealed that all the major peaks were of rhombohedral distorted perovskite structure with R3c space group. The XRD patterns showed an improvement of crystallinity with increasing sintering temperature. The morphology of the samples was studied using FESEM showed larger grain size as the sintering temperature increased, consequently increasing the multi-domain grains. The dielectric constant and dielectric loss were observed to increase corresponded to increases in grain size and are mainly due to easier domain wall movement. The capacitance values were observed to be increased when the grain size increases due to increase in sintering temperature.