skip to main content

Title: Transformation of rutile to TiO{sub 2}-II in a high pressure hydrothermal environment

The high pressure transformation of rutile to TiO{sub 2}-II with the α-PbO{sub 2} structure is known to be kinetically hindered. In this study we show that a hydrothermal environment at 6 GPa and 650 °C provides appreciable rates for producing single phase bulk samples of TiO{sub 2}-II. So obtained TiO{sub 2}-II was characterized by scanning electron microscopy, powder X-ray diffraction, Raman and Far-IR spectroscopy. The structural properties are identical to TiO{sub 2}-II from dry transitions. Transmission electron microscopy studies strongly indicate that Ostwald ripening processes play an important role in the hydrothermally assisted transformation and subsequent growth of TiO{sub 2}-II crystals. TiO{sub 2}-II is thermally stable to about 550 °C. At 600 °C the onset of the transformation to rutile is observed. The thermal expansion in the temperature range from room temperature to 500 °C is highly anisotropic, virtually affecting only the c unit cell parameter (α{sub c}=7.1(2)×10{sup −6} °C{sup −1}). The pressure–temperature conditions for the hydrothermally assisted transformation of rutile are viable for industrial production settings, and in light of the large technological significance of TiO{sub 2}, TiO{sub 2}-II may present an interesting target for large-scale synthesis. - Graphical abstract: Highly crystalline TiO{sub 2}-II, which is the high pressuremore » form of titania with the α-PbO{sub 2} structure, can be prepared from rutile at 6 GPa and 650 °C when employing a hydrothermal environment. Display Omitted.« less
Authors:
;  [1] ;  [2] ;  [1]
  1. Department of Materials and Environmental Chemistry, Stockholm University, S-10691 Stockholm (Sweden)
  2. Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604 (United States)
Publication Date:
OSTI Identifier:
22274125
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 206; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ANISOTROPY; CRYSTALS; HYDROTHERMAL SYNTHESIS; INFRARED SPECTRA; LEAD OXIDES; POWDERS; RUTILE; SCANNING ELECTRON MICROSCOPY; THERMAL EXPANSION; TITANIUM OXIDES; TRANSFORMATIONS; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION