Determining the Location and Role of Al in Al-Modified TiO2 Nanoparticles Using Low-Temperature Heat Capacity, Electron Energy-Loss Spectroscopy, and X-ray Diffraction

作者：Schliesser Jacob M; Olsen Rebecca E; Enfield David B; Woodfield Brian F^*

来源：Journal of Physical Chemistry C, 2015, 119(31): 17867-17875.

DOI：10.1021/acs.jpcc.5b04627

The location and function of clopants in metal oxide nanopartides have been poorly characterized for many systems. We have performed heat capacity measurements, electron energy-loss spectroscopy (EELS), and X-ray diffrattion (XRD) on 10 TiO2 fianoparticle samples that have different amounts of Al dopant to determine the location and function of the Al3+ cations. From the heat capacity data, lattice vacancies are observed to increase significantly with the addition of the Al dopant, suggesting Al' cations enter the TiO2 lattice and create vacancies due to the charge difference between Al3+ and Ti4O. The presence of gapped terms in fits of the lowtemperature heat capacity data also suggests that small regions of short-range order are created within the TiO2 lattice. Entropies at T = 298.15 K were determined from the heat capacity data and show effects related to the entropy of mixing, suggesting that a solid solution of Al/TiO2 is formed. EELS data confirm that Al enters the TiO2 lattice but also indicates that the short-range structure around the Al atoms shifts from a Ti02like environment toward an Al2O3-like environment as the dopant concentration increases. XRD data suggest that the long-range order of the particles decreases as the dopant concentration increases but retains a basic TiO2-like structure. This is the first investigation to use heat capacity data in this manner to determine the location of the dopant.

• 出版日期2015-8-6