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Synthesis and polymorphism of mixed aluminum-gallium oxides
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Cook, Daniel Sean, Hooper, Joseph E., Dawson, Daniel M., Fisher, Janet M., Thompsett, David, Ashbrook, Sharon E. and Walton, Richard I. (2020) Synthesis and polymorphism of mixed aluminum-gallium oxides. Inorganic Chemistry, 59 (6). pp. 3805-3816. doi:10.1021/acs.inorgchem.9b03459 ISSN 0020-1669.
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Official URL: https://doi.org/10.1021/acs.inorgchem.9b03459
Abstract
The synthesis of a new solid solution of the oxyhydroxide Ga Al O (OH) is investigated via solvothermal reaction between gallium acetylacetonate and aluminum isopropoxide in 1,4-butanediol at 240 °C. A limited compositional range of 0 ≤ ≤ 1.5 is produced, with the hexagonal unit cell parameters refined from powder X-ray diffraction (XRD) showing a linear contraction in unit cell volume with an increase in Al content. Solid-state Al and Ga nuclear magnetic resonance (NMR) spectroscopies show a strong preference for Ga to occupy the tetrahedral sites and Al to occupy the octahedral sites. Using isopropanol as the solvent, γ-Ga Al O defect spinel solid solutions with ≤ 1.8 can be prepared at 240 °C in 24 h. These materials are nanocrystalline, as evidenced by their broad diffraction profiles; however, the refined cubic lattice parameter shows a linear relationship with the Ga:Al content, and solid-state NMR spectroscopy again shows a preference for Al to occupy the octahedral sites. Thermal decomposition of Ga Al O (OH) occurs via poorly ordered materials that resemble ε-Ga Al O and κ-Ga Al O , but γ-Ga Al O transforms above 750 °C to monoclinic β-Ga Al O for 0 ≤ ≤ 1.3 and to hexagonal α-Ga Al O for = 1.8, with intermediate compositions of 1.3 < < 1.8 giving mixtures of the α- and β-polymorphs. Solid-state NMR spectroscopy shows only the expected octahedral Al for α-Ga Al O , and for β-Ga Al O , the ∼1:2 tetrahedral:octahedral Al ratio is in good agreement with the results of Rietveld analysis of the average structures against powder XRD data. Relative energies calculated by periodic density functional theory confirm that there is an ∼5.2 kJ mol penalty for tetrahedral rather than octahedral Al in Ga Al O (OH), whereas this penalty is much smaller (∼2.0 kJ mol ) for β-Ga Al O , in good qualitative agreement with the experimental NMR spectra.
Item Type: | Journal Article | ||||||||||||
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Subjects: | Q Science > QD Chemistry | ||||||||||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Chemistry | ||||||||||||
SWORD Depositor: | Library Publications Router | ||||||||||||
Library of Congress Subject Headings (LCSH): | High temperature chemistry , Polymorphism (Crystallography) , Gallium | ||||||||||||
Journal or Publication Title: | Inorganic Chemistry | ||||||||||||
Publisher: | American Chemical Society | ||||||||||||
ISSN: | 0020-1669 | ||||||||||||
Official Date: | 16 March 2020 | ||||||||||||
Dates: |
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Volume: | 59 | ||||||||||||
Number: | 6 | ||||||||||||
Page Range: | pp. 3805-3816 | ||||||||||||
DOI: | 10.1021/acs.inorgchem.9b03459 | ||||||||||||
Status: | Peer Reviewed | ||||||||||||
Publication Status: | Published | ||||||||||||
Access rights to Published version: | Open Access (Creative Commons) | ||||||||||||
Date of first compliant deposit: | 10 March 2020 | ||||||||||||
Date of first compliant Open Access: | 16 March 2020 | ||||||||||||
RIOXX Funder/Project Grant: |
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