Electronic structure and thermoelectric properties of nanostructured EuTi1−xNbxO3−δ (x = 0.00; 0.02)

The thermoelectric properties of polycrystalline nanostructured EuTiO3−δ samples are improved by a substitution of 2% Nb for Ti. The figure of merit (ZT) was measured to reach ZT(EuTi0.98Nb0.02O3−δ) ≈ 0.4 at T = 1040 K while ZT(EuTiO3−δ) ≈ 0.3 at the same temperature. X-ray photoelectron spectra reveal that the in-gap states at the Fermi level are more pronounced for the Nb-substituted samples, resulting in an improved power factor. The valence band peak below the Fermi level is sharply shaped, therefore fulfilling the condition for a large Seebeck coefficient. The specific porosity of the samples reduces the lattice thermal conductivity with a minor effect on the electron transport.