The electronic structures and thermoelectric properties of (SrO)m(SrTiO3)n superlattices have been investigated using first-principles calculations and the Boltzmann transport theory. Due to the much reduced dispersion along the c-axis, the thermoelectric properties for n-type superlattices are found to be highly anisotropic with the in-plane electrical conductivity with respect to relaxation time much higher than the out-of-plane one. The reduction of the in-plane Seebeck coefficient compared with SrTiO3 results in a slightly reduced power factor with respect to relaxation time for n-type doped (SrO)m(SrTiO3)n. However, both Seebeck coefficient and electrical conductivity with respect to relaxation time are relatively maintained for p-type doping, leading to a comparable power factor with respect to relaxation time. If the reduced thermal conductivity is taken into account, an improved ZT value can be expected for the (SrO)m(SrTiO3)n superlattice.
This work is supported by the Fundamental Research Funds for Central Universities (Grant No. 2013121010, 20720160020), the Natural Science Foundation of Fujian Province, China (Grant No. 2015J01029), Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund (the second phase), the National Natural Science Foundation of China (no. U1332105, 11335006), and the National High-tech
R&D Program of China (863 Program, No. 2014AA052202).