High-temperature thermoelectric properties of Ln(Co, Ni)O3 (Ln = La, Pr, Nd, Sm, Gd and Dy) compounds

The high-temperature thermoelectric properties of polycrystalline LnCo0.95Ni0.05O3±δ (Ln = La, Pr, Nd, Sm, Gd and Dy) compounds have been investigated. The substitution of the lanthanide element produces changes in the crystal structure and in the unit cell lattice parameters. A semiconductor to metal transition takes place for all the compounds at 500 K < T < 800 K. The transition temperature, also monitored by differential scanning calorimetry, shifts to higher temperature with the decrease in the size of the lanthanide element. The Seebeck coefficient has positive values up to T = 1240 K. The thermal conductivity is mainly dominated by the lattice contribution. The dimensionless figure of merit ZT can be enhanced at different temperatures depending on which lanthanide element occupies the A-site in the ABO3 perovskite-type phases.