Highly improved thermoelectric performance of Nb-doped SrTiO₃ due to significant suppression of phonon thermal conduction by synergetic effects of pores and metallic nanoparticles

A remarkable thermoelectric performance in oxide materials was achieved by Nb and Ni co-doped strontium titanate (STNNO) containing pores and Ni nanoparticles. A combined structure of macroporus matrix and the Ni nanoparticles was realized by an exsolution reaction of metallic Ni from the porous STNNO matrix. The porous nanocomposite structure led to a substantial decrease in the thermal conductivity down to 1.4 W m⁻¹ K⁻¹ at 800 °C, and a moderate improvement of the electrical properties. As a result, the porous nanocomposite structure containing the metallic Ni nanoparticles significantly decreased the phonon thermal conductivity to 0.91 W m⁻¹ K⁻¹ at 800 °C, resulting in a remarkable ZT of 0.60 at 800 °C for STNNO reduced in 20% H₂/N₂.