Surface segregation of BaO-doped TiO2 and its relationship with nanostability

Reference Presenter Authors
09-067 Andre Luiz da Silva da Silva, A.L.(Universidade de São Paulo); Gouvêa, D.(Universidade de São Paulo); Surface excess in nano-oxides has been demonstrated as a tool for controlling the nanoparticles stability. The direct relationship of surface segregation to surface energy and its influence on the crystallite size evolution opened new insights for understanding the role of the surface composition on nanoparticle stability. In this work, the spontaneous segregation of BaO as surface excess in BaO-doped TiO2 nanoparticles was experimentally determined by the lixiviation method. The results have shown a proportional enrichment of the dopant on the TiO2 surface as the BaO content increases. Anatase to rutile phase transition (ART) studies have demonstrated that BaO-dopant can postpone the TiO2 ART by about 200 °C. The crystallite size decreases and the specific surface area increases as the dopant content increases. Water adsorption experiment was used in order to measure the surface energy of BaO-doped TiO2. The results confirmed that the surface excess plays an important role in the system´s energetics and stability. The TiO2 surface modification was also supported by the change in the isoelectric point and by STEM-EELS.
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