Bottom-up assembly to Ag nanoparticles embedded Nb-doped TiO2 nanobulks with improved n-type thermoelectric properties

Abstract

Nb-doped TiO₂-based nanostructures were novelly prepared by an economical and environmentally friendly hydrothermal method from TiO₂ and Nb₂O₅ powder precursors. The proposed formation mechanism is acceptable for the design of various Nb-doped TiO₂-based nanostructures. Furthermore, Nb-doped TiO₂ nanostructured bulk materials (nanobulks) embedded with Ag nanoinclusions were first fabricated by the bottom-up assembly of Ag₂O nanoparticles loaded Nb-doped TiO₂-based nanostructures. The introduction of Ag nanoparticles remarkably increased the Seebeck coefficient (S) of the TiO₂ bulk ceramic by 15% to 370 μV K⁻¹ in the maximum case on account of the electron filtering effect. Moreover, their electrical conductivity (σ) was also improved by one order of magnitude up to 160 Ω⁻¹ cm⁻¹, resulting from the contribution of both introducing Ag nanoparticles and Nb-doping. Finally, the figure of merit (ZT) was increased by about two-fold owing to the substantially optimized power factors (S²σ). Our obtained results strongly confirm that the Ag embedded Nb-doped TiO₂ nanobulks can be used as good thermoelectric materials up to the high temperature of about 800 °C.