Multiferroic bismuth ferrite Bi_2Fe_4O_9 (BFO) ceramic was synthesized byconventional solid state reaction route. X-ray diffraction and Rietveldrefinement show formation of single phase ceramic with orthorhombic crystalstructure (space group Pbam). The morphological study depicted a well-definedgrain of size $\simeq$2{\mu}m. The optical studies were carried out by usingUV-Vis spectrophotometer which shows a band gap of 1.53 eV and a green emissionspectrum at 537 is observed in the Photoluminescence study. The frequencydependent dielectric study at various temperature revealed that the dielectricconstant decreases with increase in frequency. A noticeable peak shift towardshigher frequency with increasing temperature is observed in the frequencydependent dielectric loss plot. The impedance spectroscopy shows a substantialshift in imaginary impedance (Z") peaks toward the high frequency sidedescribed that the conduction in material favoring the long range motion ofmobile charge carriers. The presence of non-Debye type multiple relaxations hasbeen confirmed by complex modulus analysis. The frequency dependent acconductivity at different temperatures indicates that the conduction process isthermally activated. The variation of dc conductivity exhibited a negativetemperature coefficient of resistance behavior. The activation energycalculated from impedance, modulus and conductivity data confirmed that theoxygen vacancies play a vital role in the conduction mechanism.
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