Bottom-up assembly to Ag nanoparticles embedded Nb-doped TiO ₂ nanobulks with improved n-type thermoelectric properties

Nb-doped TiO ₂-based nanostructures were novelly prepared by an economical and environmentally friendly hydrothermal method from TiO ₂ and Nb ₂O ₅ powder precursors. The proposed formation mechanism is acceptable for the design of various Nb-doped TiO ₂-based nanostructures. Furthermore, Nb-doped TiO ₂ nanostructured bulk materials (nanobulks) embedded with Ag nanoinclusions were first fabricated by the bottom-up assembly of Ag ₂O nanoparticles loaded Nb-doped TiO ₂-based nanostructures. The introduction of Ag nanoparticles remarkably increased the Seebeck coefficient (S) of the TiO ₂ 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 (S ²σ). Our obtained results strongly confirm that the Ag embedded Nb-doped TiO ₂ nanobulks can be used as good thermoelectric materials up to the high temperature of about 800 °C.