Crystal phases, defects, and dynamics of adsorbed hyroxyl groups and water in pure and lanthanide-modified zirconia: A neutron-scattering study
- Argonne National Laboratory, IL (United States)
- Nagoya Inst. of Technology, Gifu (Japan)
The role of lanthanide doping in zirconia as a means of stabilizing and promoting catalytic reactions was studied by neutron spectroscopy. The crystal structure of high-surface-area Ln{sub 0.1}Zr{sub 0.9}O{sub 1.95}(Ln = La and Nd) powders prepared by a coprecipitation method were found to be composed of mixed phases of tetragonal and cubic symmetry, which can be stabilized over a temperature range (up to {approximately}1000{degrees}C) pertinent to catalytic applications. A real-space correlation function, obtained from a Fourier transform of the filtered residual diffuse scattering, showed evidence of static, oxygen vacancy-induced atomic displacements along the pseudocubic <111> and other directions. The dynamics of hydrogen atoms associated with the surface hydroxyl groups and adsorbed water molecules on Ln{sub 0.1}Zr{sub 0.9}O{sub 1.95} and pure ZrO{sub 2} over a frequency range of 0-4400 cm{sup -1} was investigated by neutron inelastic scattering. The stretch vibrations of surface hydroxyl groups on monoclinic ZrO{sub 2} were found to have slightly higher frequencies than those for Ln{sub 0.1}Zr{sub 0.9}O{sub 1.95}. At a submonolayer coverage of water the O-H stretch bands broaden and shift to lower energies. At higher coverage three bands, corresponding to the O-H stretch, H-O-H bend, and librational motion of water molecules, were observed, indicating the influence of hydrogen bonding. The neutron results were compared with infrared data and ab initio calculations for similar zirconia systems found in the literature. 55 refs., 7 figs., 2 tabs.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 224034
- Journal Information:
- Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 157; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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