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Interfacial stabilization of metastable TiO2 films

Gregory, Daniel G., Lu, Li, Kiely, Christopher J. and Snyder, Mark A. 2017. Interfacial stabilization of metastable TiO2 films. Journal of Physical Chemistry C 121 (8) , pp. 4434-4442. 10.1021/acs.jpcc.6b12943

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Abstract

This work demonstrates a phenomenon that preserves the traditionally metastable anatase crystal structure of thin titania (TiO2) films along a two-dimensional oxide interface at temperatures well in excess of those that normally trigger a full polymorphic transformation to rutile in higher dimensionality crystalline powders. Whereas atomic surface mobility appears to dominate polymorph transformation processes within bulk TiO2 powders, a simple reduction in dimensionality to a two-dimensional TiO2 film (ca. 50–200 nm thick), supported upon a substrate, leads to a remarkable resistance to the calcination-induced anatase-to-rutile transformation. This stabilization does not appear to be specifically reliant on substrate character given its persistence for TiO2 films prepared on amorphous silica (SiO2) as well as crystalline TiO2 substrates. Instead, interface-mediated coordination of the TiO2 film with the substrate, and the inherent confinement of crystallites in two dimensions, is believed to resist polymorph transformation by mitigation of the atomic surface mobility. Only when temperatures (i.e., >800 °C) that are conducive to bulk atomic mobilization are reached does reconstructive grain growth convert the film into the thermodynamically stable rutile crystal structure.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Cardiff Catalysis Institute (CCI)
Publisher: American Chemical Society
ISSN: 1932-7447
Date of First Compliant Deposit: 4 December 2017
Date of Acceptance: 2 February 2017
Last Modified: 02 Feb 2018 09:46
URI: http://orca-mwe.cf.ac.uk/id/eprint/107229

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