High temperature visible Raman and impedance spectroscopy of Bi-rich BiFeO3

In the present work, along with the short cut synthesis of bismuth rich BiFeO3 (BFO) ceramic, the room temperature X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Differential Scanning calorimetry (DSC), P-E loop, high temperature visible Raman and impedance spectroscopy studies are presented. XRD patterns show the prominent BFO peaks along with a few numbers of bismuth rich peaks, SEM picture shows the grain sizes in micron range, DSC results show the Neel temperature (TN) of 371°C. Room temperature Raman spectrum shows the A1 and E modes and with the increase of temperature the modes shift towards lower frequency attaining prominent red shift around TN. In impedance spectroscopy, the shift of fmax peak position towards higher frequency side of dielectric loss (tanδ) spectrums shows that the dispersion moves towards higher frequency side with the increase of temperature and activation energy calculated from Arrhenius lnfmax(1/T) plot is around 1eV for the temperature range of 240-400°C. Temperature dependent complex impedance plots (Z″ vs. Z′) reveal that at low temperature the sample is highly resistive and evolution of semicircles for both grain and grain boundary contributions start around 240°C and the depressed semicircles of both complex impedance plots and Modulus plots (M″ vs. M′) depict that the sample follows a non-Debye type process.