Significant Improvement in Electrical Conductivity and Figure of Merit of Nanoarchitectured Porous SrTiO₃ by La Doping Optimization

Abstract

SrTiO₃ is a well-studied <i>n</i>-type metal oxide based thermoelectric (TE) material. In this work, the first-principles calculation of La-doped SrTiO₃ has been performed using the density functional theory. In addition, high TE properties of bulk SrTiO₃ material have been achieved by introducing nanoscale porosity and optimizing carrier concentration by La doping. The X-ray diffraction, atomic resolution scanning transmission electron microscopy imaging, and energy-dispersive X-ray spectrometry results show that La has been doped successfully into the lattice. The scanning electron microscopy images confirm that all the samples have nearly similar nanoscale porosities. The significant enhancement of electrical conductivity over the broad temperature range has been observed through optimization of La doping. Additionally, the samples possess very low thermal conductivity, which is speculated because of the nanoscale porosity of the samples. Because of this dual mechanism of doping optimization and nanoscale porosity, there is a remarkable improvement in power factor, 1 mW/m²K from 650 to 800 K, and figure of merit, <i>zT</i> of 0.26 at 850 K, of the sample, 22 at. % La-doped SrTiO₃.