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Structural elucidation of triclinic and monoclinic SFCA-III – killing two birds with one stone
A part of the system CaO-SiO(2)–Al(2)O(3)–Fe(2)O(3)–MgO which is of relevance to iron-ore sintering has been studied in detail. For a bulk composition corresponding to 10.45 wt% CaO, 5.49 wt% MgO, 69.15 wt% Fe(2)O(3), 13.37 wt% Al(2)O(3) and 1.55 wt% SiO(2) synthesis runs have been performed in air...
Autores principales: | , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
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International Union of Crystallography
2019
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6900907/ https://www.ncbi.nlm.nih.gov/pubmed/32830692 http://dx.doi.org/10.1107/S2052520619014380 |
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author | Kahlenberg, Volker Krüger, Hannes Goettgens, Valerie Sue |
author_facet | Kahlenberg, Volker Krüger, Hannes Goettgens, Valerie Sue |
author_sort | Kahlenberg, Volker |
collection | PubMed |
description | A part of the system CaO-SiO(2)–Al(2)O(3)–Fe(2)O(3)–MgO which is of relevance to iron-ore sintering has been studied in detail. For a bulk composition corresponding to 10.45 wt% CaO, 5.49 wt% MgO, 69.15 wt% Fe(2)O(3), 13.37 wt% Al(2)O(3) and 1.55 wt% SiO(2) synthesis runs have been performed in air in the range between 1100 and 1300°C. Products have been characterized using reflected-light microscopy, electron microprobe analysis and diffraction techniques. At 1250°C, an almost phase-pure material with composition Ca(2.99)Mg(2.67)Fe(3+) (14.58)Fe(2+) (0.77)Al(4.56)Si(0.43)O(36) has been obtained. The compound corresponds to the first Si-containing representative of the M (14+6n)O(20+8n) polysomatic series of so-called SFCA phases (Silico-Ferrites of Calcium and Aluminum) with n = 2 and is denoted as SFCA-III. Single-crystal diffraction investigations using synchrotron radiation at the X06DA beamline of the Swiss Light Source revealed that the chemically homogenous sample contained both a triclinic and monoclinic polytype. Basic crystallographic data are as follows: triclinic form: a = 10.3279 (2) Å, b = 10.4340 (2) Å, c = 14.3794 (2) Å, α = 93.4888 (12)°, β = 107.3209 (14)° and γ = 109.6626 (14)°, V = 1370.49 (5) Å(3), Z = 2, space group [Image: see text]; monoclinic form: a = 10.3277 (2) Å, b = 27.0134 (4) Å, c = 10.4344 (2) Å, β = 109.668 (2)°, V = 2741.22 (9) Å(3), Z = 4, space group P2(1)/n. Structure determination of both modifications was successful using diffraction data from the same allotwinned crystal. A description of the observed polytypism within the framework of OD-theory is presented. Triclinic and monoclinic SFCA-III actually correspond to the two possible maximum degree of order structures based on OD-layers containing three spinel (S) and one pyroxene (P) modules (〈S(3)P〉). The existence of SFCA-III in industrial iron-ore sinters has yet to be confirmed. Polytypism is likely to occur in other SFCA-members (SFCA, SFCA-I) relevant to sintering as well, but has so far been neglected in the characterization of industrial samples. Our results shed light on this phenomenon and may therefore be also helpful for better interpretation of the powder diffraction patterns that are used for phase analysis of iron-ore sinters. |
format | Online Article Text |
id | pubmed-6900907 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2019 |
publisher | International Union of Crystallography |
record_format | MEDLINE/PubMed |
spelling | pubmed-69009072019-12-23 Structural elucidation of triclinic and monoclinic SFCA-III – killing two birds with one stone Kahlenberg, Volker Krüger, Hannes Goettgens, Valerie Sue Acta Crystallogr B Struct Sci Cryst Eng Mater Research Papers A part of the system CaO-SiO(2)–Al(2)O(3)–Fe(2)O(3)–MgO which is of relevance to iron-ore sintering has been studied in detail. For a bulk composition corresponding to 10.45 wt% CaO, 5.49 wt% MgO, 69.15 wt% Fe(2)O(3), 13.37 wt% Al(2)O(3) and 1.55 wt% SiO(2) synthesis runs have been performed in air in the range between 1100 and 1300°C. Products have been characterized using reflected-light microscopy, electron microprobe analysis and diffraction techniques. At 1250°C, an almost phase-pure material with composition Ca(2.99)Mg(2.67)Fe(3+) (14.58)Fe(2+) (0.77)Al(4.56)Si(0.43)O(36) has been obtained. The compound corresponds to the first Si-containing representative of the M (14+6n)O(20+8n) polysomatic series of so-called SFCA phases (Silico-Ferrites of Calcium and Aluminum) with n = 2 and is denoted as SFCA-III. Single-crystal diffraction investigations using synchrotron radiation at the X06DA beamline of the Swiss Light Source revealed that the chemically homogenous sample contained both a triclinic and monoclinic polytype. Basic crystallographic data are as follows: triclinic form: a = 10.3279 (2) Å, b = 10.4340 (2) Å, c = 14.3794 (2) Å, α = 93.4888 (12)°, β = 107.3209 (14)° and γ = 109.6626 (14)°, V = 1370.49 (5) Å(3), Z = 2, space group [Image: see text]; monoclinic form: a = 10.3277 (2) Å, b = 27.0134 (4) Å, c = 10.4344 (2) Å, β = 109.668 (2)°, V = 2741.22 (9) Å(3), Z = 4, space group P2(1)/n. Structure determination of both modifications was successful using diffraction data from the same allotwinned crystal. A description of the observed polytypism within the framework of OD-theory is presented. Triclinic and monoclinic SFCA-III actually correspond to the two possible maximum degree of order structures based on OD-layers containing three spinel (S) and one pyroxene (P) modules (〈S(3)P〉). The existence of SFCA-III in industrial iron-ore sinters has yet to be confirmed. Polytypism is likely to occur in other SFCA-members (SFCA, SFCA-I) relevant to sintering as well, but has so far been neglected in the characterization of industrial samples. Our results shed light on this phenomenon and may therefore be also helpful for better interpretation of the powder diffraction patterns that are used for phase analysis of iron-ore sinters. International Union of Crystallography 2019-11-20 /pmc/articles/PMC6900907/ /pubmed/32830692 http://dx.doi.org/10.1107/S2052520619014380 Text en © Kahlenberg et al. 2019 http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.http://creativecommons.org/licenses/by/4.0/ |
spellingShingle | Research Papers Kahlenberg, Volker Krüger, Hannes Goettgens, Valerie Sue Structural elucidation of triclinic and monoclinic SFCA-III – killing two birds with one stone |
title | Structural elucidation of triclinic and monoclinic SFCA-III – killing two birds with one stone |
title_full | Structural elucidation of triclinic and monoclinic SFCA-III – killing two birds with one stone |
title_fullStr | Structural elucidation of triclinic and monoclinic SFCA-III – killing two birds with one stone |
title_full_unstemmed | Structural elucidation of triclinic and monoclinic SFCA-III – killing two birds with one stone |
title_short | Structural elucidation of triclinic and monoclinic SFCA-III – killing two birds with one stone |
title_sort | structural elucidation of triclinic and monoclinic sfca-iii – killing two birds with one stone |
topic | Research Papers |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6900907/ https://www.ncbi.nlm.nih.gov/pubmed/32830692 http://dx.doi.org/10.1107/S2052520619014380 |
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