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|Title:||Impedance and Electric Modulus Spectroscopy of Polycrystalline La0.5Sr0.5Bi0.2Co0.4Fe0.4O3– Cathode Ceramic for Intermediate Temperature SOFCs|
Saini, Deepash Shekhar
|Keywords:||Cathode materials;Grain boundary;Porous;Impedance;Electric modulus;Jonscher’s double power law|
|Abstract:||In the present research work, La0.5Sr0.5Bi0.2Co0.4Fe0.4O3– cathode ceramic powder is synthesized through cost-effective flash pyrolysis process and followed by conventional sintering for IT-SOFCs. The Rietveld refinement program is used to determine the crystal structure, unit cell parameters and bond length. The XRD result indicates existence of a pure single phase of rhombohedral structure with R3 C space group symmetry detected from the sample sintered at 700 ℃. FESEM micrographs of fracture surface of sample sintered at 700 ℃ showed a high porosity and nano grain sizes (50-100 nm). Combined impedance and electric modulus spectroscopic are used to investigate the relaxation phenomena in La0.5Sr0.5Bi0.2Co0.4Fe0.4O3– ceramic over a broad range of temperature and frequency. A single relaxation peak is observed in the imaginary part of impedance and electric modulus spectra, which could be due to the contribution of grain boundary of La0.5Sr0.5Bi0.2Co0.4Fe0.4O3– ceramic. The imaginary part of modulus (𝑀") spectra is studied with help of non-exponential decay function or Kohlrausch–Williams–Watts (KWW) parameter (β). In the combined plot of the imaginary part of impedance (𝑍") and electric modulus (𝑀") spectra at 210 ℃, only a single peak of 𝑍"and 𝑀" is observed at the same frequency which specifies that the conduction process is a long-range motion of the charge carriers. The frequencydependent conductivity is followed by the Jonscher’s double power law in the temperature range 30-210 ℃.|
|ISSN:||0975-0959 (Online); 0301-1208 (Print)|
|Appears in Collections:||IJPAP Vol.59(08) [August 2021]|
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