Polar and non-polar structures of NH4TiOF3

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Abstract

Ammonium oxo­fluoro­titanate, NH4TiOF3, is probably the best known precursor for the synthesis of anatase mesocrystals. Transformation of NH4TiOF3 into TiO2 through thermal decomposition, accompanied by hydrolysis, preserves some structural features of the precursor. Currently, any discussion of the mechanism of this transformation is difficult, as the exact crystal structure of the starting compound is not available and no intermediate structures are known. This article describes the outcome of single-crystal and powder X-ray diffraction studies, revealing the existence of two polymorphs of the parent NH4TiOF3 at different temperatures. A second-order phase transition from the polar Pca21 α phase (1), stable at room temperature, to the Pma2 β phase (2) above ∼433 K has been demonstrated. The direction of the pseudo-fourfold axis in NH4TiOF3 coincides with the orientation of the fourfold axis of anatase mesocrystals, consistent with a topotactical transformation.

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  • Polar and non-polar structures of NH4TiOF3

    Rights statement: ©2019 International Union of Crystallography. Boytsova, O., Dovgaliuk, I., Chernyshov, D., Eliseev, A., O'Brien, P., Sutherland, A. J. & Bosak, A. (2019). J. Appl. Cryst. 52.

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Details

Original languageEnglish
Pages (from-to)23-26
Number of pages4
JournalJournal of Applied Crystallography
Volume52
Issue number1
DOIs
Publication statusPublished - 1 Jan 2019

Bibliographic note

©2019 International Union of Crystallography. Boytsova, O., Dovgaliuk, I., Chernyshov, D., Eliseev, A., O'Brien, P., Sutherland, A. J. & Bosak, A. (2019). J. Appl. Cryst. 52.

    Keywords

  • Crystal and powder X-ray diffraction, NH TiOF, Second-order phase transition

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