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http://hdl.handle.net/1843/47196| Type: | Artigo de Periódico |
| Title: | Nanocrystalline transition-metal gallium oxide spinels from acetylacetonate precursors via solvothermal synthesis |
| Authors: | Daniel Sean Cook Reza J. Kashtiban Klaus Wilhelm Heinrich Krambrock Geraldo Magela de Lima Humberto Osório Stumpf Luciano Roni Silva Lara José Domingos Ardisson Richard I. Walton |
| 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. |
| Subject: | Ferrita Cristalização Magnetismo |
| language: | eng |
| metadata.dc.publisher.country: | Brasil |
| Publisher: | Universidade Federal de Minas Gerais |
| Publisher Initials: | UFMG |
| metadata.dc.publisher.department: | ICX - DEPARTAMENTO DE FÍSICA ICX - DEPARTAMENTO DE QUÍMICA |
| Rights: | Acesso Aberto |
| metadata.dc.identifier.doi: | https://doi.org/10.3390/ma12050838 |
| URI: | http://hdl.handle.net/1843/47196 |
| Issue Date: | 12-Mar-2019 |
| metadata.dc.url.externa: | https://www.mdpi.com/1996-1944/12/5/838 |
| metadata.dc.relation.ispartof: | Materials |
| Appears in Collections: | Artigo de Periódico |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| Nanocrystalline Transition-Metal Gallium Oxide.pdf | 5.39 MB | Adobe PDF | View/Open |
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