Exfoliation and thermal transformations of Nb-substituted layered titanates

Journal Article · Thu Dec 15 00:00:00 EST 2011 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2011.08.039· OSTI ID:21612806

Haiyan, Song; Sjastad, Anja O; Fjellvag, Helmer; Okamoto, Hiroshi ^[1]; Vistad, Ornulv B; Arstad, Bjornar ^[2]; Norby, Poul ^[1]

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1. Department of Chemistry and Centre for Materials Science and Nanotechnology, University of Oslo, P.O. Box 1033, Blindern, N-0315 Oslo (Norway)
2. SINTEF Materials and Chemistry, P.O. Box 124, Blindern, N-0314 Oslo (Norway)

Single-layer Nb-substituted titanate nanosheets of ca. 1 nm thickness were obtained by exfoliating tetrabutylammonium (TBA)-intercalated Nb-substituted titanates in water. AFM images and turbidity measurements reveal that the exfoliated nanosheets crack and corrugate when sonicated. Upon heating, the thermal transformation into anatase and further to rutile is retarded. This suppression of the phase transition upon higher valent substitution may promote technological applications of anatase thin films, hereunder development of films with TCO properties. Depending on the oxygen partial pressure during the transformation, the Nb-substitution into TiO{sub 2} provokes different defect situations and also electronic properties. At reducing conditions, Nb is incorporated as Nb{sup V} and an equivalent amount of Ti{sup IV} is transformed to Ti{sup III} as evidenced by XPS. Magnetic susceptibility data show accordingly paramagnetic behavior. For samples heated in air Ti{sup IV} and Nb{sup V} cations prevail, the latter is compensated by cation vacancies. {sup 93}Nb MAS NMR data prove that Nb is finely dispersed into the transformed (Ti,Nb)O{sub 2} oxide matrices without sign of Nb{sub 2}O{sub 5} (nano)precipitates. The Nb-O-Ti bonds and defects at cation sites are considered key factors for increasing the transformation temperatures for conversion of the nanosheets to anatase and finally into rutile. It is further tempting to link the delay in crystallization to morphology limitations originating from the nanosheets. The present work shows that layered Nb-titanates are appropriate precursors for formation of highly oriented Nb-substituted anatase thin films via delamination, reconstruction and subsequent heat treatment. - Graphical abstract: Layered Nb-titanates are appropriate precursors for formation of highly oriented Nb-substituted anatase thin films via delamination, reconstruction and subsequent heat treatment. Highlights: Black-Right-Pointing-Pointer Single layer Nb-substituted nanosheets were obtained by exfoliation of layered titanates. Black-Right-Pointing-Pointer Nb(V) successfully introduced into anatase and rutile solid solutions. Black-Right-Pointing-Pointer Anatase obtained from reconstructed nanosheets exhibit enhanced thermal stability. Black-Right-Pointing-Pointer Oxygen partial pressure influences the valence of Nb in heat-treated samples. Black-Right-Pointing-Pointer Deposition of oriented thin Ti(Nb)O{sub 2} layers by spray coating was demonstrated.

• OSTI ID: 21612806
• Journal Information: Journal of Solid State Chemistry, Vol. 184, Issue 12; Other Information: DOI: 10.1016/j.jssc.2011.08.039; PII: S0022-4596(11)00479-8; Copyright (c) 2011 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
ATOMIC FORCE MICROSCOPY
CATIONS
CRYSTALLIZATION
HEAT TREATMENTS
MAGNETIC SUSCEPTIBILITY
NANOSTRUCTURES
NIOBATES
NIOBIUM 93
NIOBIUM OXIDES
NUCLEAR MAGNETIC RESONANCE
OXYGEN
PARTIAL PRESSURE
RUTILE
SOLID SOLUTIONS
SPRAY COATING
THIN FILMS
TITANATES
TITANIUM OXIDES
TRANSFORMATIONS
X-RAY PHOTOELECTRON SPECTROSCOPY
CHALCOGENIDES
CHARGED PARTICLES
DEPOSITION
DISPERSIONS
ELECTRON SPECTROSCOPY
ELEMENTS
FILMS
HOMOGENEOUS MIXTURES
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
IONS
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
MAGNETIC PROPERTIES
MAGNETIC RESONANCE
MATERIALS
MICROSCOPY
MINERALS
MIXTURES
NIOBIUM COMPOUNDS
NIOBIUM ISOTOPES
NONMETALS
NUCLEI
ODD-EVEN NUCLEI
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PHOTOELECTRON SPECTROSCOPY
PHYSICAL PROPERTIES
RADIOACTIVE MATERIALS
RADIOACTIVE MINERALS
RADIOISOTOPES
REFRACTORY METAL COMPOUNDS
RESONANCE
SOLUTIONS
SPECTROSCOPY
STABLE ISOTOPES
SURFACE COATING
THERMODYNAMIC PROPERTIES
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
YEARS LIVING RADIOISOTOPES