Suppression of thermal conductivity in LaCoO3 ceramic by lattice disorder and mass fluctuation scattering for thermoelectric application

Lanthanum Cobaltate (LaCoO3) ceramic has high seebeck coefficient (S) at room temperature which makes it a promising material for thermoelectric application, but suffer from low figure of merit (ZT) due to its large thermal conductivity (kappa). Herein, a strategy of isovalent substitution in Co site was effectively attempted to induce phonon scattering in order to decrease kappa. In this study, the perovskites were prepared by solid state reaction using corresponding metal oxide precursors at 1373 K. XRD analysis of the prepared perovskites revealed excellent phase purity and the homogeneity of the prepared samples were confirmed by HR-SEM mapping. The low kappa value of 1.38 W/mK was achieved at 753 K for Al- substituted LaCoO3. The significant decrease of thermal conductivity was due to the lattice disorder and effect of mass upon Al substitution. The strategy of isovalent substitution to achieve low thermal conductivity potentially opens up a new way for enhancing the thermoelectric performance.