Dehydration products of gypsum - positron-annihilation and dielectric measurements

dc.contributor.authorSerna Galán, Julio
dc.contributor.authorTroev, T.
dc.contributor.authorPetkov, M.
dc.contributor.authorAlemany, C.
dc.description.abstractBassanite (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.
dc.description.departmentDepto. de Óptica
dc.description.facultyFac. de Ciencias Físicas
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dc.journal.titleJournal of Materials Science
dc.publisherChapman & Hall, Ltd.
dc.rights.accessRightsmetadata only access
dc.subject.keywordMaterials Science
dc.subject.ucmÓptica (Física)
dc.subject.unesco2209.19 Óptica Física
dc.titleDehydration products of gypsum - positron-annihilation and dielectric measurements
dc.typejournal article