Determination of the structural position of Fe3+ in mullite by powder diffractometry

Fisher, O. N.; Smyslov, Yu. N.; Shmitt-Fogelevich, S. P.

doi:10.1007/bf00753202

Cited by 2 publications

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“…Peterson and McMullan (1986) observed Fe in both octahedral and tetrahedral sites in their neutron diffraction studies of sillimanite. Similar results were obtained by Fisher et al (1979) from the evaluation of intensities from powder-diffraction experiments of mullite. Mössbauer spectroscopy (Parmentier et al 1999) revealed three different Fe 3+ sites in mullite.…”

Section: Foreign Cationssupporting

confidence: 85%

A new mineral from the Bellerberg, Eifel, Germany, intermediate between mullite and sillimanite

Fischer

Tikhonova

Birkenstock

et al. 2015

American Mineralogist

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A mineral intermediate between sillimanite and mullite, tentatively designated as "sillimullite," was studied by electron microprobe analyses and single-crystal X-ray diffraction methods. The chemical compositions derived from the microprobe results and the crystal-structure refinement are Al 7.84 Fe 0.18 Ti 0.03 Mg 0.03 Si 3.92 O 19.96 and Al 8.28 Fe 0.20 Si 3.52 O 19.76 (Fe is Fe 3+ ) corresponding to x-values of 0.02 and 0.12, respectively, in the solid-solution series Al 8+4x Si 4-4x O 20-2x assigning Fe 3+ , Ti, and Mg to the Al site.The composition derived from microprobe analysis is very close to a stoichiometric sillimanite (with Fe 3+ ,Ti, and Mg assigned to Al sites), while the composition derived from diffraction data is midway between sillimanite and Si-rich mullites. The discrepancy is assumed to be caused by the occurrence of amorphous nano-sized SiO 2 inclusions in the aluminosilicate phase not affecting the diffraction data but detected in the microprobe analysis. "Sillimullite" crystallizes in the orthorhombic space group Pnam with a = 7.5127(4), b = 7.6823(4), c = 5.785(3) Å, V = 333.88(4) Å 3 , Z = 1. It has a complete Si/Al ordering at tetrahedral sites like sillimanite but with neighboring double chains of SiO 4 and AlO 4 tetrahedra being offset by ½ unit cell parallel to c relative to each other causing the change of the space-group setting from Pbnm (sillimanite) to Pnam. Difference Fourier calculations and refinements with anisotropic displacement parameters revealed the formation of oxygen vacancies and triclusters as known in the crystal structures of mullite. Final refinements converged at R1 = 5.9% for 1024 unique reflections with F o > 4s(F o ). Fe was found to reside predominantly in the octahedral site and with minor amounts in one of the T* sites. Mg and Ti were not considered in the refinements. The crystal studied here is considered to represent a new mineral intermediate between sillimanite and mullite, named "sillimullite."

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Section: Foreign Cationssupporting

confidence: 85%

A new mineral from the Bellerberg, Eifel, Germany, intermediate between mullite and sillimanite

Fischer

Tikhonova

Birkenstock

et al. 2015

American Mineralogist

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“…Besides this, the Fe 3+, Ti 4+, Ti s+ atoms and others [3,13,26] can occupy the tetrahedral and octahedral positions and can also be incorporated in the statistically distributed structural channels that are located parallel to the c axis and form due to the displacement of A1 atoms during the creation of oxygen vacancies.…”

Section: All-union Institute Of Refractories (Viomentioning

confidence: 99%

“…In sillimanite, the type (i) substitution leads to a mullite structure having a statistical (random) distribution of oxygen vacancies [] [8,9,13]. The following structural formula of mullite was previously suggested [Ii]:…”

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confidence: 99%

“…According to this diagram, mullite is the only aluminosilicate that is stable at high temperatures. It was established [5][6][7][8][9][10][11][12][13] that the solid solutions of mullite whose composition changes from 3A1203"2Si02 up to 2A!203"Si02 are obtained as a result of a heterovalent substitution 2Si~++C~--~-~2AI~++ 0.In sillimanite, the type (i) substitution leads to a mullite structure having a statistical (random) distribution of oxygen vacancies [] [8, 9, 13]. The following structural formula of mullite was previously suggested [Ii]:…”

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Phase and chemical analysis of a fused refractory based on bauxite concentrate

Соколов¹,

Казаков²,

Tsiporina³

et al. 1987

Refractories

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Bauxite concentrate is a promising raw material for producing high-alumina refractories that are used in the ladles designed for out-of-furnace treatment of steels [i].The purpose of this work is to study the structure and the properties of the fused refractories made from a bauxite concentrate obtained by hydrochloric acid treatment [2].Mullite-based solid solutions (having a basicity >1.5) constitute the main crystalline phase of the refractories obtained from bauxite and its concentrate [2][3][4]. The phase diagram of the AI203-SiO2 system gives an approximate phase constitution of the aluminosilicate refractories (including the fused refractories) as a functionof the chemical composition. According to this diagram, mullite is the only aluminosilicate that is stable at high temperatures. It was established [5][6][7][8][9][10][11][12][13] that the solid solutions of mullite whose composition changes from 3A1203"2Si02 up to 2A!203"Si02 are obtained as a result of a heterovalent substitution 2Si~++C~--~-~2AI~++ 0.In sillimanite, the type (i) substitution leads to a mullite structure having a statistical (random) distribution of oxygen vacancies [] [8, 9, 13]. The following structural formula of mullite was previously suggested [Ii]:where AIVI and AIIV indicate the coordination~ (sites) of aluminum atoms in the octahedral and tetrahedral positions, respectively; and x is the number of oxygen atoms lost per unit structural cell of sillimanite. Cameron [10][11][12] noted that sucha scheme of isomorphous substitution does not restrict the extent of mullitic solid solutions right up to sillimanite [14] on one hand and up to aluminum oxide [15][16][17][18] on the other.The possibility of obtaining mullites of variable composition by electromelting alumina and silica was shown earlier [19].Electromelting of bauxite concentrate and the compositions of the Al2Os-bauxite concentrate-SiO 2 system was carried out in a 'Kristall' unit using a cold crucible having an internal diameter of 65 mm. In order to melt (cast) the specimens of this system, we used high purity (99.99%) aluminum oxide and silica. Electromelting was carried out in air by successive fusion of AI203 and the mixtures of A1203, bauxite concentrate, and silica and an ingot measuring approximately 600 mm in length was obtained. Samples were cut out from the external region of the ingot using a diamond tool. The ingot was subjected to the maximum cooling rate (10-20~ Phase analysis of aluminosilicate refractories is difficult because not only chemical, but also crystallographic transformations occur during the process of their production. In view of this, the methods of rational chemical and x-ray phase analysis are of limited use because chemical analysis requires corrections for the solubility of the phase being analyzed as a function of the particle size, the temperature, and the duration of acid treatment; and x-ray phase analysis needs corrections for the degree of crystallinity of the phases. These facts prompted the application of infrared spectroscopy.Qu...

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Determination of the structural position of Fe3+ in mullite by powder diffractometry

Cited by 2 publications

References 0 publications

A new mineral from the Bellerberg, Eifel, Germany, intermediate between mullite and sillimanite

A new mineral from the Bellerberg, Eifel, Germany, intermediate between mullite and sillimanite

Phase and chemical analysis of a fused refractory based on bauxite concentrate

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