Improvement of thermoelectric performance of oxygen reduced Sr 0.7 Ba 0.3 Nb 2 O 6-δ ceramics by Lanthanides doping

Thermoelectric properties of lantanide doped Sr 0.7 Ba 0.3 Nb 2 O 6 ceramics were investigated in the temperature range from 323 K to 1073 K. A better electrical conductivity is obtained in the sample with larger ionic radius of doping element. Thus, the highest PF value is achieved in La-doped sample. The NbO 2 second phase is counterproductive to reduce the lattice thermal conductivity, so La-doped sample without impurity shows low thermal conductivity. Thus, La-doped sample shows an excellent thermoelectric performance ZT ∼ 0.35. The small average grain size and the nano-sized phases are observed in Gd and Dy doped samples, both of which contribute to scattering phonons, resulting in low thermal conductivities.