Probing vacancy-type free-volume defects in Li2B4O7 single crystal by positron annihilation lifetime spectroscopy. (January 2018)

• Record Type: Journal Article
• Authors: Shpotyuk, O.; Adamiv, V.; Teslyuk, I.; Ingram, A.; Demchenko, P.
• Is Part Of: Journal of physics and chemistry of solids. Volume 112(2018)
• Page Start: 8
• Page End: 13
• Publication Date: 2018-01
• Subjects: Lithium tetraborate -- Positron annihilation lifetime -- Positronium -- Trapping -- Vacancy; Solids -- Periodicals; Solides -- Périodiques; Solids; Periodicals; 530.41
• DOI: 10.1016/j.jpcs.2017.08.025
• Languages: English
• ISSNs: 0022-3697

Abstract

Abstract: Vacancy-type free-volume defects in lithium tetraborate Li2 B4 O7 single crystal, grown by the Czochralski technique, are probed with positron annihilation spectroscopy in the lifetime measuring mode. The experimental positron lifetime spectrum is reconstructed within the three-component fitting, involving channels of positron and positronium Ps trapping, as well as within the two-component fitting with a positronium-compensating source input. Structural configurations of the most efficient positron traps are considered using the crystallographic specificity of lithium tetraborate with the main accent on cation-type vacancies. Possible channels of positron trapping are visualized using the electronic structure calculations with density functional theory at the basis of structural parameters proper to Li2 B4 O7 . Spatially-extended positron-trapping complexes involving singly-ionized lithium vacancies, with character lifetime close to 0.32 ns, are responsible for positron trapping in the nominally undoped lithium tetraborate Li2 B4 O7 crystal. Highlights: Positron annihilation in Li2 B4 O7 crystal due to mixed positron-positronium trapping. Decisive role of positron trapping in lithium tetraborate single crystal. Defect-related positron lifetime close to 0.317 ns in Li2 B4 O7 crystal. Defect sites involving singly-ionized Li + vacancies responsible for positron trapping.