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Nanocrystalline transition-metal gallium oxide spinels from acetylacetonate precursors via solvothermal synthesis
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Cook, Daniel Sean, Kashtiban, Reza J., Krambrock, Klaus, de Lima, Geraldo, Stumpf, Humberto, Lara, Luciano, Ardisson, José and Walton, Richard I. (2019) Nanocrystalline transition-metal gallium oxide spinels from acetylacetonate precursors via solvothermal synthesis. Materials, 12 (5). 838. doi:10.3390/ma12050838 ISSN 1996-1944.
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Official URL: http://dx.doi.org/10.3390/ma12050838
Abstract
The synthesis of mixed-metal spinels based on substituted γ-Ga2O3 is reported using metal acetylacetonate precursors in solvothermal reactions with alcohols as solvents at 240 °C. New oxides of Cr, Mn and Fe have been produced, all of which are formed as nanocrystalline powders, as seen by high-resolution transmission electron microscopy (HR-TEM). The first chromium-gallium mixed oxide is thus formed, with composition 0.33Ga1.87Cr0.8O4 ( = vacant site). X-ray absorption near-edge spectroscopy (XANES) at the chromium K-edge shows the presence of solely octahedral Cr3+, which in turn implies a mixture of tetrahedral and octahedral Ga3+, and the material is stable on annealing to at least 850 °C. An analogous manganese material with average chemical composition close to MnGa2O4 is shown to contain octahedral Mn2+, along with some Mn3+, but a different inversion factor to materials reported by conventional solid-state synthesis in the literature, which are known to have a significant proportion of tetrahedral Mn2+. In the case of iron, higher amounts of the transition metal can be included to give an Fe:Ga ratio of 1:1. Elemental mapping using energy dispersive X-ray spectroscopy on the TEM, however, reveals inhomogeneity in the distribution of the two metals. This is consistent with variable temperature 57Fe Mössbauer spectroscopy that shows the presence of Fe2+ and Fe3+ in more than one phase in the sample. Variable temperature magnetisation and electron paramagnetic resonance (EPR) indicate the presence of superparamagnetism at room temperature in the iron-gallium oxides. View Full-Text
Item Type: | Journal Article | ||||||||||||
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Subjects: | Q Science > QD Chemistry | ||||||||||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Chemistry | ||||||||||||
Library of Congress Subject Headings (LCSH): | Transition metal compounds, Gallium, Spinel group | ||||||||||||
Journal or Publication Title: | Materials | ||||||||||||
Publisher: | M D P I AG | ||||||||||||
ISSN: | 1996-1944 | ||||||||||||
Official Date: | 12 March 2019 | ||||||||||||
Dates: |
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Volume: | 12 | ||||||||||||
Number: | 5 | ||||||||||||
Article Number: | 838 | ||||||||||||
DOI: | 10.3390/ma12050838 | ||||||||||||
Status: | Peer Reviewed | ||||||||||||
Publication Status: | Published | ||||||||||||
Access rights to Published version: | Open Access (Creative Commons) | ||||||||||||
Description: | This article belongs to the Special Issue Green and Unconventional Routes for the Synthesis of Crystalline Inorganic Materials —Selected Papers from AIM 2018) |
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Date of first compliant deposit: | 7 May 2019 | ||||||||||||
Date of first compliant Open Access: | 9 May 2019 | ||||||||||||
RIOXX Funder/Project Grant: |
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