Thermoelectric properties of Li-doped Sr_0.7Ba_0.3Nb₂O_6-δ ceramics

Thermoelectric properties of Li-doped Sr_0.70Ba_0.30Nb₂O_6-δ ceramics were investigated in the temperature range from 323 K to 1073 K. The electrical conductivity increases significantly after lithium interstitial doping. However, both of the magnitudes of Seebeck coefficient and electrical conductivity vary non-monotonically but synchronously with the doping contents, indicating that doped lithium ions may not be fully ionized and oxygen vacancy may also contribute to carriers. The lattice thermal conductivity increases firstly and then decreases as the doping content increases, which is affected by competing factors.Thermoelectric performance is enhanced by lithium interstitial doping due to the increase of the power factor and the thermoelectric figure of merit reaches maximum value (0.21 at 1073 K) in the sample Sr_0.70Ba_0.30Li_0.10Nb₂O₆.