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Structures of uncharacterised polymorphs of gallium oxide from Total neutron diffraction
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Playford, Helen Y., Hannon, Alex C., Barney, Emma R. and Walton, Richard I. (2013) Structures of uncharacterised polymorphs of gallium oxide from Total neutron diffraction. Chemistry - A European Journal, Volume 19 (Number 8). pp. 2803-2813. doi:10.1002/chem.201203359 ISSN 0947-6539.
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Official URL: http://dx.doi.org/10.1002/chem.201203359
Abstract
A structural investigation is reported of polymorphs of Ga2O3 that, despite much interest in their properties, have hitherto remained uncharacterised due to structural disorder. The most crystalline sample yet reported of γ-Ga2O3 was prepared by solvothermal oxidation of gallium metal in ethanolamine. Structure refinement using the Rietveld method reveals γ-Ga2O3 has a defect Fdequation imagem spinel structure, while pair distribution function analysis shows that the short-range structure is better modelled with local Fequation image3m symmetry. In further solvothermal oxidation reactions a novel gallium oxyhydroxide, Ga5O7(OH), is formed, the thermal decomposition of which reveals a new, transient gallium oxide polymorph, κ-Ga2O3, before transformation into β-Ga2O3. In contrast, the thermal decomposition of Ga(NO3)3⋅9 H2O first forms ε-Ga2O3 and then β-Ga2O3. Examination of in situ thermodiffraction data shows that ε-Ga2O3 is always contaminated with β-Ga2O3 and with this knowledge a model for its structure was deduced and refined—space group P63mc with a ratio of tetrahedral/octahedral gallium of 2.2:1 in close-packed oxide layers. Importantly, thermodiffraction provides no evidence for the existence of the speculated bixbyite structured δ-Ga2O3; at the early stages of thermal decomposition of Ga(NO3)3⋅9 H2O the first distinct phase formed is merely small particles of ε-Ga2O3.
Item Type: | Journal Article | ||||
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Divisions: | Faculty of Science, Engineering and Medicine > Science > Chemistry | ||||
Journal or Publication Title: | Chemistry - A European Journal | ||||
Publisher: | Wiley - V C H Verlag GmbH & Co. KGaA | ||||
ISSN: | 0947-6539 | ||||
Official Date: | February 2013 | ||||
Dates: |
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Volume: | Volume 19 | ||||
Number: | Number 8 | ||||
Page Range: | pp. 2803-2813 | ||||
DOI: | 10.1002/chem.201203359 | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published | ||||
Access rights to Published version: | Restricted or Subscription Access |
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