Structural, Raman and dielectric behavior in Bi1−xSrxFeO3 multiferroic

The effect of Sr2+ doping on Bi1−xSrxFeO3 (x = 0.0, 0.15, 0.175, 0.25) multiferroic ceramics synthesized by citrate sol–gel method has been investigated by Rietveld analysis of X-ray powder diffraction data, Raman spectroscopy and dielectric measurement. X-ray diffraction along with the Rietveld-refinement showed a gradual change in crystal structure from rhombohedral (R3c) to pseudotetragonal (P4/mmm) with enhanced divalent Sr2+ ion concentration. All the 13 Raman modes predicted by group theory (ΓR3c = 4A1 + 9E) for R3c structure of Bi1−xSrxFeO3 (x = 0.0, 0.15, 0.175, 0.25) were observed in the present study. The A1-2 and E-4 modes are completely suppressed, while that of A1-3, E-8 mode in Bi1−xSrxFeO3 (x = 0.175, 0.25) and E-2, E-5, and E-8 modes (x = 0.25) disappear completely as compared to parent BFO. The structural phase transition and weakening of long-range ferroelectric order with increasing doping concentration are thus further confirmed from Raman scattering spectra. The dielectric anomaly has been observed in dielectric constant and dielectric loss near 325 °C, 305 °C, 270 °C and 250 °C (f = 10 kHz) in BiFeO3, Bi0.85Sr0.15FeO3, Bi0.825Sr0.175FeO3 and Bi0.75Sr0.25FeO3, respectively.