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

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 mu VK-1 in the maximum case on account of the electron filtering effect. Moreover, their electrical conductivity (sigma) was also improved by one order of magnitude up to 160 Omega(-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-2 sigma). 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 degrees C.