RT Journal Article
T1 Dehydration products of gypsum - positron-annihilation and dielectric measurements
A1 Serna Galán, Julio
A1 Troev, T.
A1 Petkov, M.
A1 Alemany, C.
AB Bassanite (CaSO_4•½ H_2O) and anhydrite (CaSO_4) are the low-temperature products of gypsum (CaSO_4·2H_2O) 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.
PB Chapman & Hall, Ltd.
SN 0022-2461
YR 1994
FD 1994-02-15
LK https://hdl.handle.net/20.500.14352/58603
UL https://hdl.handle.net/20.500.14352/58603
DS Docta Complutense
RD 10 abr 2025