Journal of Materials Science

, Volume 29, Issue 4, pp 865–869 | Cite as

Dehydration products of gypsum: positron annihilation and dielectric measurements

  • T. Troev
  • M. Petkov
  • C. Alemany
  • J. Serna


Bassanite (CaSO4·1/2 H2O) and anhydrite (CaSO4) are the low-temperature products of gypsum (CaSO4·2H2O) dehydration, which are obtained at about 373 and 433 K, respectively. These sulphates have non-centrosymmetric crystallographic point groups, but dielectric measurements do not reveal any piezo- or ferroelectric characteristic, and they practically behave like linear dielectrics. Positron lifetime spectra exhibit the existence of two different positron states, besides a free positron state. There is positronium formation in the three sulphates, and there is also evidence for the presence of a highly populated positron bound state which may be a complex state associated with positrons bound to SO 4 2− ions. Parameter S estimated from the Doppler curve and the average positron lifetime show unquestionably the sensitivity of positrons to the phase transitions gypsum-bassanite and bassanite-anhydrite.


Gypsum Anhydrite CaSO4 Positron Annihilation Dielectric Measurement 
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Copyright information

© Chapman & Hall 1994

Authors and Affiliations

  • T. Troev
    • 1
  • M. Petkov
    • 1
  • C. Alemany
    • 2
  • J. Serna
    • 3
  1. 1.Institute for Nuclear Research and Nuclear EnergyBulgarian Academy of SciencesSofiaBulgaria
  2. 2.Instituto de Ciencia de Materiales (Sede A)CSICMadridSpain
  3. 3.Departamento de Física de Materiales, Facultad de Ciencias FísicasUniversidad ComplutenseMadridSpain

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