Transformation of rutile to TiO2-II in a high pressure hydrothermal environment
2013 (English)In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 206, 209-216 p.Article in journal (Refereed) Published
The high pressure transformation of rutile to TiO2-II with the α-PbO2 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 TiO2-II. So obtained TiO2-II was characterized by scanning electron microscopy, powder X-ray diffraction, Raman and Far-IR spectroscopy. The structural properties are identical to TiO2-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 TiO2-II crystals. TiO2-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 (αc=7.1(2)×10−6 °C−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 TiO2, TiO2-II may present an interesting target for large-scale synthesis.
Place, publisher, year, edition, pages
2013. Vol. 206, 209-216 p.
Titania, High pressure polymorphism, Hydrothermal synthesis, Multi anvil techniques
Research subject Materials Chemistry
IdentifiersURN: urn:nbn:se:su:diva-123998DOI: 10.1016/j.jssc.2013.08.018ISI: 000326007800032OAI: oai:DiVA.org:su-123998DiVA: diva2:881085