Electronic excitations and self-trapping of electrons and holes in $CaSO_4$

Kudryavtseva, I.; Lushchik, A.; Lushchik, Ch; Klopov, M.; Pishtshev, A.; Maaroos, A.

doi:10.1088/0031-8949/89/4/044013

Journal Article

PUBDB-2015-01929

Electronic excitations and self-trapping of electrons and holes in $CaSO_4$

Kudryavtseva, I. ; Klopov, M. ; Lushchik, A. (Corresponding Author)>Extern* ; Lushchik, C. ; Maaroos, A. ; Pishtshev, A.

2014
IoP Publ. Bristol

Physica scripta 89(4), 044013 (2014) [10.1088/0031-8949/89/4/044013]

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Please use a persistent id in citations: doi:10.1088/0031-8949/89/4/044013

Abstract: A first-principles study of the electronic properties of a CaSO4 anhydrite structural phase has been performed. A theoretical estimation for the fundamental band gap (p → s transitions) is Eg = 9.6 eV and a proper threshold for p → d transitions is Epd = 10.8 eV. These values agree with the data obtained for a set of CaSO4 doped with Gd3+, Dy3+, Tm3+ and Tb3+ ions using the methods of low-temperature highly sensitive luminescence and thermoactivation spectroscopy. The results are consistent with theoretical predictions of a possible low-temperature self-trapping of oxygen p-holes. The hopping diffusion of hole polarons starts above ~40 K and is accompanied by a ~50–60 K peak of thermally stimulated luminescence of RE3+ ions caused due to the recombination of hole polarons with the electrons localized at RE3+. There is no direct evidence of the self-trapping of heavy d-electrons, however, one can argue that their motion rather differs from that of conduction s-electrons.

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