Aliovalent Doping of Ceria IT-SOFC Electrolyte: Structural, Morphological, Electrical and Transport Properties

A nanocrystalline solid solution of Ceria co-doped with Samarium, Strontium, and Calcium with composition Ce0.8Sm0.2-x-ySryCaxO2-delta (x = y = 0-0.5) samples pellets were synthesized via solid-state reaction method and sintered at 1300 degrees C intended to be an electrolyte of IT-SOFC. X-ray diffraction (XRD) confirms the crystalline nature with an fcc fluorite structure. Williamson-hall plots were used to find the microstrain and particle size. Scanning electron microscopy (SEM) was employed for surface morphology with microstructure and found to be nearly spherical particles with porosity, the Energy Dispersive Spectroscopy analysis (EDAX) with color mapping confirmed the stoichiometry. The sample pellets were analyzed using impedance spectroscopy by impedance spectra, where an AC voltage is applied in the range of frequency 1 Hz-10 MHz to record the impedance in the temperature ranging from 300 to 800 degrees C in the air as a medium. Electrical parameters such as the dielectric constant, epsilon'r, and AC conductivity, sigma ac have been found. The samples show a negative temperature coefficient of resistance, where the grain boundary conductivity is increased with increasing temperatures showing a peak in the conductivity curve which is also evident from the Nyquist plot for impedance.