Industrial Applications

Bare, Simon R.; Cutler, Jeffrey

doi:10.1002/9781118844243.ch24

Cited by 1 publication

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“…K-edge XANES spectra of Fe, Cr, and V of spinels are analyzed in order to correlate the characteristics of the pre-edge feature with the oxidation state and coordination number of the investigated atoms by comparing them to various model compounds (Bunnag et al, 2020;Wilke et al, 2001). The pre-edge feature is related to the metal electronic transitions 1s → 3d (quadrupolar) and/or 1s → 4p (dipolar) (Westre et al, 1997), and its position shifts toward higher oxidation state (Bare, 2007;Newville, 2014;Ravel, 2015;Ruiz, 2011;Westre et al, 1997;Wilke et al, 2001;Wilke et al, 2005).…”

Section: Photoluminescence Spectroscopymentioning

confidence: 99%

“…EXAFS is used to characterize the distance, coordination number, the types of surrounding atoms, and the level of disorder, whereas XANES is an effective spectroscopic method for determining oxidation state and structural symmetry. The shift of the absorption edge ( edge energy, E0) and distinctive XANES characteristics are affected by a probed element with various oxidation states and local structure(Bare, 2007;Newville, 2014; Ravel, 2015;Ruiz, 2011). As previously stated, this has induced our research to investigate gem-quality colored tanzanite and spinel for clarifying their mechanism of color-causing role.…”

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Trace elements and color-causing role in spinel and tanzanite

Pluthametwisute

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This research is aimed to investigate the significant trace elements and their color-causing roles in tanzanite and spinels (7 color varieties) by focusing on their concentrations, valencies, and site occupancy�since no palpable research has been reported previously either before or after heating of both gems. According to this finding, natural tanzanites usually show strongly trichroic colors of violet, blue, and brown in different directions. However, this characteristic is easily changed to violet-blue dichroism after heat treatment. As the result, the violet-blue absorption band (centered around 450460 nm) is obviously decreased after heating, and XAS analysis indicates the higher valency state of vanadium. Consequently, vanadium is strongly suggested as the significant coloring agent in tanzanite which is also supported by its dominant concentration. Based on this finding, natural spinels contain trace elements which may cause various hues. Red color is attributed by the combination of significant Cr and V ratios. Magenta and purple to blue and green colors are affected by significant Fe content, whereas orange color shows contribution to significant V content. After heating, XAS indicates a greater oxidation state as well as disordering of iron and vanadium, while Cr stays consistent. Broadening of the dominant peak at around 406.2 cm-1�and the occurrence of additional small peak at around 715.2-719.8 cm-1�in Raman spectra as well as broadening of the 685 nm and poorly defined structure of additional peaks in photoluminescence spectra are significant indicators of inverse spinels (heated spinel) which strongly benefits gem-testing laboratory to recognize the heat-treated spinel. �

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Section: Photoluminescence Spectroscopymentioning

confidence: 99%

mentioning

confidence: 99%

Trace elements and color-causing role in spinel and tanzanite

Pluthametwisute

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Industrial Applications

Cited by 1 publication

References 121 publications

Trace elements and color-causing role in spinel and tanzanite

Trace elements and color-causing role in spinel and tanzanite

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