High performance (ZT>1) n-type oxide thermoelectric composites from earth abundant materials

Oxide-based thermoelectric materials have the advantages of high-temperature stability, low toxicity and low processing cost comparted to other metal-based systems. However, achieving ZT > 1 remain elusive especially for n-type bulk oxide thermoelectrics. Here, we report the experimental demonstration of ZT > 1 in n-type oxides by synthesizing composites of Nb-doped SrTiO3 (STN) with natural graphite. Introduction of conductive graphite inclusions in STN matrix has led to a surge in electrical conductivity due to 21-times increase in weighted mobility (mu(w)) of electrons resulting in high thermoelectric power factor similar to 5400 mu W/mK(2), which is similar to 16-times higher than that of pure STN. Furthermore, we could restrain the increase in thermal conductivity by attaining enhanced Umklapp scattering along with phonon-glass-like temperature-independent phonon mean-free-path above Debye temperature. We have achieved the maximum ZT similar to 1.42 in STN+ 0.5 wt% G composite, which is 15-times enhancement compared to STN. Our proposed way of designing rare-earth-free composites with graphite can potentially open up the possibility of fabricating novel high-temperature thermoelectric generators.

Automated summary

This study experimentally demonstrated the achievement of ZT > 1 in n-type oxides, significantly increasing electrical conductivity and thermoelectric power factor through composite material synthesis. Additionally, thermal conductivity was effectively controlled by improving scattering mechanisms and phonon transport, leading to enhanced ZT values.