Floating Zone Growth of Oxides and Metallic Alloys

Several metal oxide compounds, especially those containing metals possessing several valence states, are able to absorb or release oxygen under suitable thermodynamic conditions. Such behavior is found often in systems containing oxides of transition metals. It is important to note that the equilibrium oxidation level of those metal oxides can depend on the aggregation state, which may significantly impede crystal growth processes from the melt. If during the melt growth of such oxide crystals, the average valence state of the oxides is different in the molten and solid state, then crystallization is connected with the absorption of free oxygen from the ambient gas, or with the release of free oxygen into it. This phenomenon can be detected by simultaneous DTA/TG measurements and can deteriorate the stability of crystal growth. This holds especially if the average valence in the solid is smaller than in the melt, because oxygen release can lead to bubble formation at the crystallization front.

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Raman Spectroscopy of Natural Titanomagnetites

HULIJELI,

WATANABE,

NISHIKAWA

et al. 2022

Int.J.Soc.Mater.Eng.Resour.

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The Raman spectral patterns of analyzed natural titanomagnetite samples revealed peaks at 670-680 cm -1 , 544-603 cm -1 , 407-495 cm -1 and 373-392 cm -1 that correspond to the A 1g , T 2g (2), T 2g (3) and E g vibrational modes of the spinel Fd3m space group. Previous studies of titanomagnetite Raman spectra patterns have suggested the behavior of these peaks refl ect the distribution of Fe 2+ -O, Fe 3+ -O and Ti 4+ -O bonds within the titanomagnetite crystal structure. The peak intensities of each vibrational modes are observed to be relative, reflecting the re-distribution of Fe 2+ and Fe 3+ in both the tetrahedral and octahedral sites as a function of Ti concentration. Existing titanomagnetite Raman spectroscopy studies are limited to analysis of synthetic titanomagnetite. In this study, Raman spectral patterns from natural titanomagnetite i.e., magnetite-ulvöspinel solid solution samples were analyzed to determine behavior of Raman spectrum peak positions and intensities due to changing content of Ti 4+ , Fe 2+ and Fe 3+ .

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Floating Zone Growth of Oxides and Metallic Alloys

Cited by 3 publications

References 226 publications

Growth of β-Ga2O3 crystal with a diameter of 30 mm by laser-diode-heated floating zone (LDFZ) method

Growth of β-Ga2O3 crystal with a diameter of 30 mm by laser-diode-heated floating zone (LDFZ) method

On Thermodynamic Aspects of Oxide Crystal Growth

Raman Spectroscopy of Natural Titanomagnetites

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