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

SrTiO3 is a well-studied n-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, zT of 0.26 at 850 K, of the sample, 22 at. % La-doped SrTiO3.

Enhancing the Thermoelectric Performance of Polycrystalline SnSe by Decoupling Electrical and Thermal Transport through Carbon Fiber Incorporation.

Thermoelectric (TE) materials have attracted extensive interest because of their ability to achieve direct heat-to-electricity conversion. They provide an appealing renewable energy source in a variety of applications by harvesting waste heat. The record-breaking figure of merit reported for single crystal SnSe has stimulated related research on its polycrystalline counterpart. Boosting the TE conversion efficiency requires increases in the power factor and decreases in thermal conductivity. It is still a big challenge, however, to optimize these parameters independently because of their complex interrelationships. Herein, we propose an innovative approach to decouple electrical and thermal transport by incorporating carbon fiber (CF) into polycrystalline SnSe. We show that the incorporation of highly conductive CF can successfully enhance the electrical conductivity, while greatly reducing the thermal conductivity of polycrystalline SnSe. As a result, a high TE figure-of-merit (zT) of 1.3 at 823 K is obtained in p-type SnSe/CF composite polycrystalline materials. Furthermore, SnSe samples incorporated with CFs exhibit superior mechanical properties, which are favorable for device fabrication applications. Our results indicate that the dispersion of CF can be a good way to greatly improve both TE and mechanical performance.