UV optical absorption spectra analysis of spodumene crystals from Brazil

Isotani, Sadao; Watari, K.; Mizukami, Akiyoshi; Bonventi, Waldemar; Ito, Amando Siuiti

doi:10.1016/j.physb.2006.10.015

Cited by 14 publications

(11 citation statements)

References 22 publications

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“…The intensity of spin-allowed IVCT transitions depends more on the populations of the cation pairs in adjacent sites rather than on concentrations of individual cations, considering the error in the absorption intensities (3%). 15 The correlation illustrated in Figure 2 No direct correlations between the content of FeO alone (without TiO 2 ) and the absorption coefficient were found. After this data a possible indication for two groups of green and green-brown tourmalines was observed.…”

Section: Further Statistical Analyses Using Chemical and Spectrophotomentioning

confidence: 91%

The Ti-influence on the tourmaline color

Fonseca-Zang¹,

Zang²,

Hofmeister³

2008

J. Braz. Chem. Soc.

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Titânio em turmalinas pretas foi analisado por espectrofotometria entre 12500 e 27000 cm -1 (800-370 nm) em um microscópio MPV-5P, Leitz (Alemanha), e analisado quimicamente em uma micro-sonda eletrônica Camebax Microbeam, Cameca (France) (WDS-mode). Quatorze turmalinas orientadas com faces paralelas ao eixo trigonal, cortadas e polidas até espessuras finas mostraram, em espectros polarizados, duas bandas largas de absorbância a aproximadamente 14000 cm -1 (715 nm) e 24000 cm -1 (417 nm). Medidas de espessura das amostras foram usadas no cálculo de coeficientes de absorção α (cm -1 ). Para a banda em torno de 24000 cm -1 (417 nm), foi observada uma correlação linear entre α e a concentração em massa de TiO 2 (%). Outra regressão foi observada entre α e o produto da concentração em massa de TiO 2 (%) e FeO (%). Cátions localizados em grupos de octaedros Y e Z conectados através dos seus lados podem contribuir para as transferências de carga Ti 3+ -Ti 4+ , Fe 2+ -Ti 4+ , Ti 3+ -Ti 4+ -Fe 3+ .Titanium was examined in different black tourmalines by spectrophotometric analyses in the region between 12500 and 27000 cm -1 (800-370 nm) using a microscope spectrophotometer MPV-5P, Leitz (Germany), and chemically analyzed on an electron microprobe Camebax Microbeam, Cameca (France) in WDS Mode. Fourteen tourmaline samples with their face oriented parallel to the principal axis, cut and polished down to thin sections, showed polarized spectra of two broad absorption bands at approximately 14000 cm -1 (715 nm) and 24000 cm -1 (417 nm). Precision thickness measurements were used to calculate the absorption coefficients α. For the absorption around 24000 cm -1 , a linear correlation was observed between α and the TiO 2 content (mass %). Another linear regression was observed between α and the product of TiO 2 and FeO (%) contents. Cations located in the Y-and Z-octahedrons of the structure that are connected over edges might contribute to intervalence charge transfer transitions (IVCT) between Ti 3+ -Ti 4+ , Fe 2+ -Ti 4+ and Ti 3+ -Ti 4+ -Fe 3+ .

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Section: Further Statistical Analyses Using Chemical and Spectrophotomentioning

confidence: 91%

The Ti-influence on the tourmaline color

Fonseca-Zang¹,

Zang²,

Hofmeister³

2008

J. Braz. Chem. Soc.

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“…Finally, ghost lines can arise from weak non-Gaussian components introduced by any problem with the polarization detector nonlinearity and saturation, dispersing the sample surface defects due to polishing among other factors. So, we made spectral decomposition using as reference for the decomposition process applied prior to the absorption spectra of spodumene [15] and beryl [10].…”

Section: The 1931 Cie Chromaticity Diagram Calculationsmentioning

confidence: 99%

“…The parameters of (6), ν 0i , Δν i , and a i , were determined using a grid optimization method [26]. This method was applied to optimize the decomposition of the spectra of spodumene [15] and beryl [10]. The procedure makes use of a grid in the parameter space obtained by changing each parameter back and forth and calculating robust cost functions on the surfaces of this grid.…”

Section: The 1931 Cie Chromaticity Diagram Calculationsmentioning

confidence: 99%

“…In the present study, we did the calculation of the chromatic coordinates, using the absorbance described as the sum of absorption lines. We applied the decomposition process described in previous reports [10,15] to determine the parameters of these lines from the spectrum of absorbance shown in Figure 1. Figure 1 shows the optical absorption spectrum of a Brazilian blue topaz of an irradiated sample submitted to heat treatment at 200 • C for 24 hours.…”

Section: Spectral Decomposition Analysismentioning

confidence: 99%

“…Gemological quality crystals of beryl, quartz, spodumene, topaz, and tourmaline among many others, constitute an important economic resource for the Eastern Brazilian Pegmatite Province [4]. The optical absorption spectra of crystals of the Province of Oriental Brazilian Pegmatite were reported by several authors for beryl [5][6][7][8][9][10], amethyst [11], spodumene [12][13][14][15], topaz [16][17][18][19][20][21][22][23][24], and tourmaline [25].…”

Section: Introductionmentioning

confidence: 99%

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Color Dependence on Thickness in Topaz Crystal from Brazil

Bonventi

Isotani

Albuquerque

2012

Advances in Condensed Matter Physics

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It is well known that crystals of topaz from the Eastern Brazilian Pegmatite Province may turn blue by the irradiation with 60 Co gamma rays followed by heat treatment. Also, it is known that the sensation of color changes with the thickness of these crystals. The dependence of the color, given by 1931 CIE chromaticity coordinates, with the thickness of the crystal was analyzed. The absorbance used in the calculation of these coordinates was given by the sum of Gaussian lines. The parameters of these lines were determined through the decomposition of the optical absorption spectra in the ultraviolet and visible regions. The decomposition revealed several lines, whose assignment was made considering studies in spodumene and beryl crystals and highly accurate quantum mechanical calculations. The transmittance becomes very narrow with increasing thickness, and the CIE chromaticity coordinates converge to the borderline of the CIE Chromaticity Diagram at the wavelength of maximum transmittance. Furthermore, the purity of color increases with increasing thickness, and the dominant wavelength reaches the wavelength of maximum transmittance.

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First-principles calculations of electronic structures and optical, phononic, and thermodynamic properties of monoclinic α -spodumene

Duan

et al. 2017

Ceramics International

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UV optical absorption spectra analysis of spodumene crystals from Brazil

Cited by 14 publications

References 22 publications

The Ti-influence on the tourmaline color

The Ti-influence on the tourmaline color

Color Dependence on Thickness in Topaz Crystal from Brazil

First-principles calculations of electronic structures and optical, phononic, and thermodynamic properties of monoclinic α -spodumene

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