La-doped SmBaCuFeO 5 polycrystalline ceramics have been prepared through sol-gel method followed by solid-state sintering reaction. A significant enhancement in the thermoelectric properties of SmBaCuFeO 5 has been achieved by La doping. Our results reveal that the La doping can lead to a remarkable increase in the electrical conductivity of 2 orders of magnitude. The Seebeck coefficient decreases with increasing La content, which is consistent with the increased electrical conductivity. Thermal conductivity at room temperature decreases from 2.1 W m-1 K-1 to 1.7 W m-1 K-1 due to the existence of nano-sized grains in the high substitutive content samples. The maximum ZT of 0.042 at 1023 K is obtained for Sm 0.6 La 0.4 BaCuFeO 5 , which is 13 times more than that of the pristine sample. © 2014 Elsevier Ltd. All rights reserved.