'Unusual Ln{sup 3+} substitutional defects': The local chemical environment of Pr{sup 3+} and Nd{sup 3+} in nanocrystalline TiO{sub 2} by Ln-K edge EXAFS

Journal Article · Thu Nov 15 00:00:00 EST 2007 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2007.09.025· OSTI ID:21043755

Ghigna, Paolo ^[1]; Speghini, Adolfo; Bettinelli, Marco ^[2]

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1. Dipartimento di Chimica Fisica 'M. Rolla', Universita di Pavia, Viale Taramelli 16, I-27100 Pavia (Italy)
2. Dipartimento Scientifico e Tecnologico, Universita di Verona and INSTM, UdR Verona, Ca' Vignal, Strada Le Grazie 15, I-37134 Verona (Italy)

The local chemical environment of the trivalent lanthanide cations in anatase TiO{sub 2} nanopowders doped with 1 mol% of Pr or Nd, prepared via a sol-gel technique, has been studied by means of EXAFS at the Pr and Nd-K edge. Titanium dioxide can be considered an 'unusual' host for doping with Ln{sup 3+} ions due to the large mismatch of both charge and ionic radii between the dopant and the host constituent cations. However, it can be demonstrated that the lanthanide ions enter the anatase structure as substitutional defects with respect to Ti, but that the amount of disorder around the substitutional defects is very large. For both Pr{sup 3+} and Nd{sup 3+} ions, the Ln-O and Ln-Ti distances have been found to increase by about 0.45 A, with respect to what is found for the Ti-O and Ti-Ti distances in pure anatase. Valence-bond calculations have been used to validate the Ln-O distances obtained by the EXAFS fitting. Finally, no evidences for oxygen vacancies clustering around the substitutional defects have been found. Luminescence spectroscopy has shown that the lanthanide ions do not segregate in oxide or pyrochlore impurities phases. - Graphical abstract: Comparison between the room temperature emission spectra of the Nd{sup 3+} doped TiO{sub 2} nanocrystalline sample (a), the Nd{sub 2}Ti{sub 2}O{sub 7} sample (b) and a commercial Nd{sub 2}O{sub 3} sample (c) ({lambda}{sub exc}=355 nm)

• OSTI ID: 21043755
• Journal Information: Journal of Solid State Chemistry, Vol. 180, Issue 11; Other Information: DOI: 10.1016/j.jssc.2007.09.025; PII: S0022-4596(07)00400-8; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ABSORPTION SPECTROSCOPY
CATIONS
CRYSTALS
DOPED MATERIALS
EMISSION SPECTRA
FINE STRUCTURE
LUMINESCENCE
NANOSTRUCTURES
NEODYMIUM IONS
NEODYMIUM OXIDES
PRASEODYMIUM IONS
PYROCHLORE
SOL-GEL PROCESS
TEMPERATURE RANGE 0273-0400 K
TITANATES
TITANIUM OXIDES
VACANCIES
X-RAY SPECTROSCOPY