Pressure-induced amorphization and a possible polyamorphism transition in nanosized TiO2:: An x-ray absorption spectroscopy study

被引:35
作者
Flank, A. -M. [1 ]
Lagarde, P. [1 ]
Itie, J. -P. [1 ]
Polian, A. [2 ]
Hearne, G. R. [3 ]
机构
[1] SOLEIL Synchrotron, F-91192 Gif Sur Yvette, France
[2] Univ Paris 06, CNRS, IMPMC, Phys Milieux Denses, F-75015 Paris, France
[3] Univ Witwatersrand, Sch Phys & DST NRF CoE Strong Mat, Johannesburg, South Africa
来源
PHYSICAL REVIEW B | 2008年 / 77卷 / 22期
关键词
D O I
10.1103/PhysRevB.77.224112
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
The phenomenon of grain-size dependent pressure-induced amorphization (PIA) in TiO(2) nanomaterials has been evidenced by several experiments in recent years. This has stemmed mainly from x-ray diffraction (XRD) and Raman studies of ultrafine grained anatase. Until now there is no experimental evidence of the length scale of disorder nor is there a clear picture of the amorphous structures, specifically in the case of pressure amorphised anatase-TiO(2) starting material. The unresolved issues of the structural details and atomic-scale picture of the high-density amorphous (HDA) phase have now been addressed in an x-ray absorption spectroscopy (XAS) pressure study at the Ti K-edge. The local environment of the cation, to within a few nearest-neighbor shells, has been monitored up to similar to 30 GPa where the HDA phase is stabilized. In this phase the titanium atom is surrounded by 3 +/- 0.5 oxygens at 1.89 angstrom and 3 +/- 0.5 oxygens at 2.07 angstrom. The XAS results of this study suggest that a precursor ordered structural phase, different to that of anatase, is prevalent before amorphization occurs. The nature of this high-pressure stabilized precursor to amorphization likely depends on the starting experimental conditions at ambient pressure. In some cases this precursor has been identified as the columbite (alpha-PbO(2)-type) crystalline structure perhaps with only limited range order. Samples of this type appear to evidence a "memory effect" in that after cycling into the HDA phase (up to 30 GPa) where complete structural disorder prevails, this alpha-PbO(2) structural intermediate is reestablished in a limited pressure range of the decompression cycle. It is also found that a new structure is stabilized in all cases of samples decompressed from the HDA phase to ambient conditions, characterized by fivefold coordinated Ti (2 +/- 0.5 oxygens at 1.84 angstrom and 2.5 +/- 0.5 oxygens at 2.06 angstrom) and is therefore structurally distinguishable from the HDA phase. These conceptual pictures are derived from the pressure dependence of both the extended x-ray-absorption fine structure (EXAFS) and the preedge parts of the absorption spectra.
引用
收藏
页数:9
相关论文
共 22 条
[1]   High-pressure polymorphs of anatase TiO2 [J].
Arlt, T ;
Bermejo, M ;
Blanco, MA ;
Gerward, L ;
Jiang, JZ ;
Olsen, JS ;
Recio, JM .
PHYSICAL REVIEW B, 2000, 61 (21) :14414-14419
[2]   High-pressure structural phases of titanium dioxide [J].
Dewhurst, JK ;
Lowther, JE .
PHYSICAL REVIEW B, 1996, 54 (06) :R3673-R3675
[3]   Ti K-edge XANES studies of Ti coordination and disorder in oxide compounds: Comparison between theory and experiment [J].
Farges, F ;
Brown, GE ;
Rehr, JJ .
PHYSICAL REVIEW B, 1997, 56 (04) :1809-1819
[4]   LUCIA, a microfocus soft XAS beamline [J].
Flank, AM ;
Cauchon, G ;
Lagarde, P ;
Bac, S ;
Janousch, M ;
Wetter, R ;
Dubuisson, JM ;
Idir, M ;
Langlois, F ;
Moreno, T ;
Vantelon, D .
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS, 2006, 246 (01) :269-274
[5]  
FRANKLIN P, 2004, THESIS U WITWATERSRA
[6]   Effect of grain size on structural transitions in anatase TiO2:: A Raman spectroscopy study at high pressure -: art. no. 134102 [J].
Hearne, GR ;
Zhao, J ;
Dawe, AM ;
Pischedda, V ;
Maaza, M ;
Nieuwoudt, MK ;
Kibasomba, P ;
Nemraoui, O ;
Comins, JD ;
Witcomb, MJ .
PHYSICAL REVIEW B, 2004, 70 (13) :134102-1
[7]   Pressure-induced disappearance of the local rhombohedral distortion in BaTiO3 [J].
Itié, JP ;
Couzinet, B ;
Polian, A ;
Flank, AM ;
Lagarde, P .
EUROPHYSICS LETTERS, 2006, 74 (04) :706-711
[8]   HIGH-PRESSURE POLYMORPHISM OF TITANIUM DIOXIDE [J].
JAMIESON, JC ;
OLINGER, B .
SCIENCE, 1968, 161 (3844) :893-&
[9]   Electron population analysis by full-potential X-ray absorption simulations [J].
Joly, Y ;
Cabaret, D ;
Renevier, H ;
Natoli, CR .
PHYSICAL REVIEW LETTERS, 1999, 82 (11) :2398-2401
[10]   Interpretation of absorption edges by resonant electronic spectroscopy:: experiment and theory [J].
Le Fèvre, P ;
Magnan, H ;
Chandesris, D ;
Jupille, J ;
Bourgeois, S ;
Drube, W ;
Ogasawara, H ;
Uozumi, T ;
Kotani, A .
JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA, 2004, 136 (1-2) :37-47