| In this thesis, perovskite oxide SrTiO3, a new kind of thermoelectric materials, is selected as the object of this study. Nanocrystallization and doping are both analyzed to find the possibility of enhancing the thermoelectric performance of SrTiO3. Main contents of each chapter are as follows:In chapter I, we proposed a model of SrTiO3ceramics with two-dimensional electron gas (2DEG) grain boundaries (GBs). The simulation results show this material exhibits a large thermoelectric figure of merit by utilizing quantum confinement and energy filtering at GBs. The calculated transport coefficients indicated that phonon confinement at grain interior (GI) and GBs greatly reduces the lattice thermal conductivity, and quantum confinement2DEG at GBs greatly enhances the power factor. The energy filtering effect on electrons and boundary scattering of phonons at GBs furtherly enhance the ZT value. Based on simulation results, we firstly prepared the GB-Nb-5%La-SrTiO3nanocubes with a size of under20nm, which were adopted to prepare the nanocrystalline ceramics by spark plasma sintering (SPS) technique. The results showed this kind of nanostructuring can effectively reduce the lattice thermal conductivity of SrTiO3bulk materials due to the increased interfacial thermal resistivity. At the same time, the Nb-doped grain boundaries were considered to play a positive role in enhancing the Seebeck coefficient for the bulk ceramics, possibly by the energy filtering effect. Therefore, the nanostructured SrTiO3-based3D superlattice can be taken as a kind of promising thermoelectric materials.In chapter II, the self-assemble behavior of SrTiO-3nanounits in the formation of the bulk materials under ambient conditions was discussed. Firstly, a self-assembled-monolayers (SAMs) modified anodic aluminum oxide (AAO) membranes were used to generate crystalline strontium titanate (SrTiO3) nanotube arrays. The possible formation mechanism can be explained by the induced nucleation effect of the functional headgroups in the SAMs. Then, SrTiO3nanoplates arrays were obtained by the precipitation of an aqueous gel suspension. The amount of additive oleic acid played a significant role in the formation of pure SrTiO3phase with specific morphologies. The results of TEM and ED investigations provided evidences that the oriented aggregation of small nanocubes is the dominant growth mechanism for the formation of the observed SrTiO3nanoplates. The primary nanocrystals were self-assembled in a highly oriented fashion, producing defective single-crystal particles. The present study would be expected to the realization of3D nanostructured thermoelectric bulk materials which could give rise to high-efficiency thermal-to-electric energy conversion materials through a quantum size effect.In chapter â…¢, we proposed dye-sensitized solar cell/thermoelectric generator hybrid device. The suitable nanostructured mutilayer films can optimize the efficiency of the device. Based on that, a novel and effective method for the preparation of nanostructured (SiO2-like/TiO2/SiO2-like)n mutilayer films on the flexible polymer substrate at room temperature was persented. The as-prepared films are composed of porous SiO2-like layers and dense TiO2layers. By precisely controlling the thickness and the number of layers, the films can selectively reflect the near infrared light. This facile synthesis of nanostructured (SiO2-like/TiO2/SiO2-like)n mutilayer films has a great potential for the development of thermoelectric device and dye-sensitized solar cells.
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