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Structural phase transition and high temperature phase structure of Friedels salt, 3CaO dot Al2O3 dot CaCl2 dot 10H2O
Friedels salt, the chlorinated compound 3CaO dot Al2O3 dot CaCl2 dot 10H2O (AFm phase), presents a structural phase transition at about 30 degree C from a monoclinic to a rhombohedral phase. It has been studied by X-ray powder diffraction and optical microscopy in transmitted light with crossed polarizers on single crystals prepared by hydrothermal synthesis. The high temperature phase was determined at 37 degree C from X-ray single crystal diffraction data. The compound crystallizes in the space group R3 over bar c with lattice parameters of a = 5.7358(6) angstroms and c = 46.849(9) angstroms (Z = 3 and Dx = 2.111 g/cm3). The refinement of 498 independent reflections with I>2 sigma(I) led to a residual factor of 7.1%. The Friedels salt can be described as a layered structure with positively charged main layers of composition (Ca2Al(OH)6)+ and negatively charged layers of composition (Cl-,2H2O). The chloride anions are surrounded by 10 hydrogen atoms, of which six belong to hydroxyl groups and four to water molecules. The structural phase transition may be related to the size of the chloride anions, which are not adapted to the octahedral cavity formed by bonded water molecules.
Structural phase transition and high temperature phase structure of Friedels salt, 3CaO dot Al2O3 dot CaCl2 dot 10H2O
Friedels salt, the chlorinated compound 3CaO dot Al2O3 dot CaCl2 dot 10H2O (AFm phase), presents a structural phase transition at about 30 degree C from a monoclinic to a rhombohedral phase. It has been studied by X-ray powder diffraction and optical microscopy in transmitted light with crossed polarizers on single crystals prepared by hydrothermal synthesis. The high temperature phase was determined at 37 degree C from X-ray single crystal diffraction data. The compound crystallizes in the space group R3 over bar c with lattice parameters of a = 5.7358(6) angstroms and c = 46.849(9) angstroms (Z = 3 and Dx = 2.111 g/cm3). The refinement of 498 independent reflections with I>2 sigma(I) led to a residual factor of 7.1%. The Friedels salt can be described as a layered structure with positively charged main layers of composition (Ca2Al(OH)6)+ and negatively charged layers of composition (Cl-,2H2O). The chloride anions are surrounded by 10 hydrogen atoms, of which six belong to hydroxyl groups and four to water molecules. The structural phase transition may be related to the size of the chloride anions, which are not adapted to the octahedral cavity formed by bonded water molecules.
Structural phase transition and high temperature phase structure of Friedels salt, 3CaO dot Al2O3 dot CaCl2 dot 10H2O
Renaudin, G. (author) / Kubel, F. (author) / Rivera, J.P. (author) / Francois, M. (author)
Cement and Concrete Research ; 29 ; 1937-1942
1999
6 Seiten, 13 Quellen
Article (Journal)
English
Formation and stability of 3CaO dot CaCl2 dot 12H2O
| Tema Archive | 2001
| British Library Online Contents | 1999
| Taylor & Francis Verlag | 2019