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On Polymorphism of BaAl2Si2O8

  • W. F. Müller

Abstract

The polymorphs of BaAl2Si2O8 known so far are celsian, paracelsian and hexacelsian. Celsian is a monoclinic feldspar mineral with a 14 Å c-axis and a body-centered lattice (Newnham and Megaw, 1960). Paracelsian, which also occurs as a mineral, has a framework structure similar to the feldspar structure (Smith, 1953; Bakakin and Belov, 1961; Craig et al., 1973). Hexacelsian, which is only known as a synthetic product is a layer alumosilicate built up by double sheets of Al2Si2O8 (Ito, 1950). Takéuchi (1958) described a hexagonal and an orthorhombic polytype. According to Lin and Foster (1968), celsian is stable at atmospheric pressure below 1590° C. From 1590° C up to the melting point (~ 1760° C) hexacelsian, is the stable polymorph. It persists metastably when cooled below 1590° C. Paracelsian appears to be a metastable phase.

Keywords

Electron Diffraction Pattern Antiphase Domain Stable Polymorph Transmission Electron Microscopic Method Composition Plane 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. Allpress, J.G., Sanders, J.V.: The direct observation of the structure of real crystals by lattice imaging. J. Appl. Cryst. 6, 165–190 (1973).CrossRefGoogle Scholar
  2. Bahat, D.: Kinetic study on the hexacelsian-celsian phase transformation. J. Mat. Sci. 5, 805–810(1970).CrossRefGoogle Scholar
  3. Bakakin, V.V., Below, N.V.: Crystal structure of paracelsian. Soviet. Phys.-Cryst. 5, 826–829 (1961).Google Scholar
  4. Craig, J.R., Louisnathan, S.J., Gibbs, G.V.: Al/Si order in paracelsian. EOS, Transactions Austr. Geoph. Union 54, 497 (1973).Google Scholar
  5. Ito, T.: X-ray studies on polymorphism. Tokyo: Maruzen 1950.Google Scholar
  6. Lin, H.C., Foster, W.R.: Studies in the system BaO-Al2O3-SiO2 I. The polymorphism of celsian. Am. Mineralogist 53, 134–144 (1968).Google Scholar
  7. Müller, W.F.: Antiphase domains in CaAl2Si2O8 (anorthite), SrAl2Si2O8 and BaAl2Si2O8. Proc. 8th Int. Congress on Electron Microscopy, Canberra, 1, 472–473 (1974).Google Scholar
  8. Newnham, R.E., Megaw, H.D.: The crystal structure of celsian (barium feldspar). Acta Cryst. 13, 303–312(1960).CrossRefGoogle Scholar
  9. Smith, J.V.: The crystal structure of paracelsian, BaAl2Si2O8. Acta Cryst. 6, 613–620 (1953).CrossRefGoogle Scholar
  10. Takéuchi, Y.: A detailed investigation of the structure of hexagonal BaAl2Si2O8 with reference to its α-ß inversion. Mineral. J. (Sapporo) 2, 311–332 (1958).Google Scholar

Copyright information

© Springer-Verlag Berlin · Heidelberg 1976

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  • W. F. Müller

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