Effect of A-site doping on electrical properties of La2-xPrxFeCoO6 double perovskite prepared by sol-gel technique

Abstract

The present work deals with the synthesis, characterization, and thermoelectric properties of La2-xPrxFeCoO6 (x ​= ​0.0, 0.25, 0.50, 0.75, and 1.0) ceramics. The crystal structure, microstructural characteristics, electrical properties, and thermal transport characteristics of the sintered samples were studied. The samples prepared by sol-gel technique resulted in the presence of nanocrystalline single phase material after 6 ​h of sintering, and the increased crystallite size with increasing Pr concentration alongwith the occurrences of multivalent oxidation states of La, Pr, Fe, Co and O. The conductivity investigation revealed the presence of a nearest neighbor hopping charge carrier conduction mechanism in the entire samples, i.e., an increasing Pr-content result in enhanced conductivity at every examined temperature. For the entire composition range (x), conductivity increases with increasing temperature up to maximum value at a transition temperature followed by a downward trend, indicating the metallic behavior (reduction in semiconducting behavior) due to the presence of oxygen deficiency at higher temperature. Positive S values indicate the presence of p-type charge carrier in La2-xPrxFeCoO6 double perovskite and intrinsic behavior was conserved with increasing doping concentration (x). Temperature dependent power factor increases with increasing Pr-content and the maximum values were observed at their transition temperatures. Within recorded temperature, the highest Figure of Merit (ZT ​= ​∼0.87) was observed at x ​= ​1.0 in La2-xPrxFeCoO6 compound, which was 5.4 times more as compare to x ​= ​0.0.