Enhancement of thermoelectric performance of Sr0.7Ba0.3Nb2O6−δ ceramics by lanthanum doping

Thermoelectric properties of La doped Sr0.7Ba0.3Nb2O6-δ ceramics were investigated in the temperature range from 323 K to 1073 K. The electrical resistivity decreases due to the subsitution of La for Sr, leading to the enhancement of thermoelectric power factor in the heavily doped sample Sr0.50La0.20Ba0.30Nb2O6−δ. Slight La-doping promotes the growth of Sr0.7Ba0.3Nb2O6−δ grains, but it will be impeded in the heavily La doped samples. Thus, La heavily doped sample Sr0.50La0.20Ba0.30Nb2O6−δ shows low thermal conductivity because of the phonon scattering caused by grain boundaries. The highest thermoelectric performance was observed in the sample Sr0.50La0.20Ba0.30Nb2O6−δ, and the thermoelectric figure of merit reaches the maximum value ~0.22 at 1073 K.