Improvement of the thermoelectric properties of substituted SrTiO$_{3}$ by synthesis conditions*

We have studied thermoelectric properties of polycrystalline Sr$_{1-x}$La$_{x}$TiO$_{3}$ and SrTi$_{1-x}$Nb$_{x}$O$_{3}$ (x$<$=0.2) synthesized by a solid state synthesis method in a H$_{2}$/Ar atmosphere. The incorporation of La and Nb into the crystal structure was confirmed by x-ray diffraction and energy dispersive x-ray spectroscopy. By increasing the synthesis temperature (up to $\sim $1570$^{o}$C) and decreasing the partial pressure of oxygen, we were able to optimize the thermoelectric properties of the studied materials. The determined values of the thermoelectric figure of merit ZT$\sim $0.1 at 400 K and $\sim $0.3 at 800 K are comparable to those of single crystals of La- and Nb- substituted compounds. Our results show that the synthesis conditions play a crucial role in tailoring of the thermoelectric properties of substituted strontium titanates.