Abstract
In this study, effect of Ca-doping on electrical and electrochemical properties of garnet structure Y3-xCaxFe5O12-δ (x = 0, 0.05, 0.1, 0.3, 0.5 and 0.7) was investigated. Cubic-phase (Ia-3d) garnet was prepared through sol-gel method and sintered at 1100 °C for 2 h in air. Highest oxygen non-stoichiometry (δ = 0.19) was found in x = 0.3 member. X-ray absorption spectroscopy (XAS) confirmed the formation of hole carriers () due to Ca-substitution for Y in Y3Fe5O12. 4-Probe DC measurements showed that electrical conductivity increased with an increase in Ca amount until x = 0.1 (1.58 S/cm at 750 °C) and then decreased due to decrease in the concentration of the charge carriers. Lowest area specific resistance (ASR) of 1 Ωcm2 was seen at 750 °C in air for the symmetrical cell with x = 0.3 garnet-LSGM composite electrode. Studies on pO2 dependent ASR and impedance spectroscopy genetic programming (ISGP) analysis revealed that oxygen dissociation and partial reduction of adsorbed oxygen molecule co-limit the electrochemical performance for oxygen reduction reaction (ORR).