Thermoelectric properties of Sr and Mg double-substituted LaCoO3 at room temperature

A strategy to improve the thermoelectric properties of LaCoO3 by the double substitution of Sr and Mg in La1−xSrxCo1−xMgxO3 (x=0, 0.025, 0.05, 0.1) is presented. Effects of either Sr or Mg substitution are also investigated separately in the series of La1−xSrxCoO3 and LaCo1−xMgxO3 (x=0, 0.02, 0.05, 0.1, 0.2). All the samples were successfully synthesized by the citrate sol-gel method. Replacing La by a small amount of Sr increases electronic conductivity but decreases the Seebeck coefficient; the decrease in the Seebeck coefficient is reduced when Mg is simultaneously substituted for Co. The employment of both Sr and Mg substitutions benefit to the enhancement in thermoelectric efficiency since both electrical conductivity and Seebeck coefficient are enhanced while thermal conductivity is suppressed. With this strategy, a sample with a small amount of double substitution, which is typically La0.975Sr0.025Co0.0975Mg0.025O3, exhibits a ZT of 0.047 at room temperature.