| Abstract
| - Mesosporous pure anatase TiO2 optical thin films, exhibiting 35% volume porosity, more than 100 m2·g-1 surface area, and organized mesostructure, have been stabilized by careful delayed rapid crystallization (DRC) thermal treatments up to 700 °C. The initial Im3m body center cubic undergoes a transformation involving pore fusion in the [111] directions.
- TiO2 optical thin films stable to 700 °C, exhibiting 35% volume porosity, more than 100m2·g-1 in surface area, fully nanocrystalline anatase framework, and organized mesostructure(cubic Im3m derived), have been stabilized by careful delayed rapid crystallization (DRC)thermal treatments. In-situ time-resolved SAXS and WAXS investigations were simultaneously performed during such treatments. They revealed that a slow and progressive heatingto a temperature just below that of the formation of anatase (Tc ≈ 400 °C), followed by along pretreatment at this temperature, stabilizes the amorphous network. A following rapidincrease of temperature up to temperatures as high as typically 700 °C, followed by a shortresidence time at this high temperature, provokes the homogeneous formation of crystallinesmall nanoparticles and the total elimination of organic residues. The crystallization isaccompanied by matter migration through diffusing sintering and pore merging along the[111] directions of the cubic structure, leading to a novel grid-like mesostructure with openporosity. This DRC treatment allows the preparation of highly porous and crystalline anatasefilms, with thermal stability 200 °C higher than previously reported, that are ideal for energytransfer applications. This emphasizes the role of the treatment method to stabilize transitionmetal oxide mesoporous materials over extended crystallization at high temperatures. Thesefilms exhibit excellent long time stability below 500 °C.
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