Correlation of microstructural and physical properties in bulk BiFeO3 prepared by rapid liquid-phase sintering

BiFeO3 sample prepared by rapid liquid phase sintering (RLPS) technique is found to posses better dielectric properties than the subsequently annealed sample. These samples also show ferromagnetism at room temperature. Detailed X-ray diffraction and Rietveld refinement of the data show that oxygen–iron–oxygen (O–Fe–O) bond angle is considerably more distorted in samples prepared by rapid liquid-phase sintering technique than in the annealed sample. In addition, synchrotron X-ray diffraction as well as high resolution transmission electron microscopy studies show higher concentration of impurity phases in the annealed samples, which is the likely reason for inferior dielectric properties. Further transmission electron microscopy results indicate that high crystalline order is not necessary for better dielectric properties. However weak ferromagnetism is observed in all these samples and appears to be the intrinsic property of samples prepared by rapid liquid phase sintering technique.

X-ray diffraction pattern of two samples of BiFeO3 (a) prepared by rapid liquid phase sintering (RLPS) technique and (b) Subsequently annealed sample, obtained using synchrotron X-ray source. Respective inset shows a comparison of the X-ray diffraction pattern of both the samples obtained using lab and synchrotron X-ray source. The absence of Fe2O3 peaks is indicated in both (a) and (b) graphs by the dashed lines (vertical). Presence of Bi2O3 peaks in BFOS sample is shown in figure (b) by ‘*’. Peaks from secondary phases are shown by ‘#’.Figure optionsDownload as PowerPoint slideHighlights
► BiFeO3 sample prepared by rapid liquid phase sintering (RLPS) technique.
► Sample prepared by this method have low dielectric losses.
► Ferromagnetism at room temperature appears to be intrinsic to these samples.
► Sample prepared by this method is not in chemical equilibrium state.
► Sintering sample increases impurity phases deteriorating dielectric properties.