Nanocrystalline transition-metal gallium oxide spinels from acetylacetonate precursors via solvothermal synthesis

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dc.creatorDaniel Sean Cook
dc.creatorReza J. Kashtiban
dc.creatorKlaus Wilhelm Heinrich Krambrock
dc.creatorGeraldo Magela de Lima
dc.creatorHumberto Osório Stumpf
dc.creatorLuciano Roni Silva Lara
dc.creatorJosé Domingos Ardisson
dc.creatorRichard I. Walton
dc.date.accessioned2022-11-11T18:52:07Z
dc.date.accessioned2025-09-08T23:57:09Z
dc.date.available2022-11-11T18:52:07Z
dc.date.issued2019-03-12
dc.format.mimetypepdf
dc.format.mimetypepdf
dc.identifier.doihttps://doi.org/10.3390/ma12050838
dc.identifier.issn19961944
dc.identifier.urihttps://hdl.handle.net/1843/47196
dc.languageeng
dc.publisherUniversidade Federal de Minas Gerais
dc.relation.ispartofMaterials
dc.rightsAcesso Aberto
dc.subjectFerrita
dc.subjectCristalização
dc.subjectMagnetismo
dc.subject.otherFerrite
dc.subject.otherCrystallisation
dc.subject.otherMagnetism
dc.subject.otherXANES
dc.subject.otherMössbauer spectroscopy
dc.subject.otherEPR
dc.titleNanocrystalline transition-metal gallium oxide spinels from acetylacetonate precursors via solvothermal synthesis
dc.typeArtigo de periódico
local.citation.epage16
local.citation.issue5
local.citation.spage1
local.citation.volume12
local.description.resumoThe 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.
local.identifier.orcidhttps://orcid.org/0000-0002-3871-1647
local.identifier.orcidhttps://orcid.org/0000-0002-7562-0285
local.publisher.countryBrasil
local.publisher.departmentICX - DEPARTAMENTO DE FÍSICA
local.publisher.departmentICX - DEPARTAMENTO DE QUÍMICA
local.publisher.initialsUFMG
local.url.externahttps://www.mdpi.com/1996-1944/12/5/838

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