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Scientific article
English

Structural phase transition and high temperature phase structure of Friedels salt, 3CaO · Al2O3 · CaCl2 · 10H2O

Published inCement and concrete research, vol. 29, no. 12, p. 1937-1942
Publication date1999
Abstract

Friedels salt, the chlorinated compound 3CaO · Al2O3 · CaCl2 · 10H2O (AFm phase), presents a structural phase transition at about 30°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 polarisers on single crystals prepared by hydrothermal synthesis. The high temperature phase was determined at 37°C from X-ray single crystal diffraction data. The compound crystallises in the space group RFull-size image (<1 K)c with lattice parameters of Full-size image (<1 K). The refinement of 498 independent reflections with I > 2σ(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.

Keywords
  • Crystal structure
  • X-ray diffraction
  • Chloride
  • Friedels salt
  • Structural transition
Citation (ISO format)
RENAUDIN, Guillaume et al. Structural phase transition and high temperature phase structure of Friedels salt, 3CaO · Al2O3 · CaCl2 · 10H2O. In: Cement and concrete research, 1999, vol. 29, n° 12, p. 1937–1942. doi: 10.1016/S0008-8846(99)00199-4
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ISSN of the journal0008-8846
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