Positronics of subnanometer atomistic imperfections in solids as a high-informative structure characterization tool

Abstract

Methodological possibilities of positron annihilation lifetime (PAL) spectroscopy applied to characterize different types of nanomaterials treated within three-term fitting procedure are critically reconsidered. In contrast to conventional three-term analysis based on admixed positron- and positronium-trapping modes, the process of nanostructurization is considered as substitutional positron-positronium trapping within the same host matrix. Developed formalism allows estimate interfacial void volumes responsible for positron trapping and characteristic bulk positron lifetimes in nanoparticle-affected inhomogeneous media. This algorithm was well justified at the example of thermally induced nanostructurization occurring in 80GeSe2-20Ga2Se3 glass.

Water-Sorption Effects near Grain Boundaries in Modified MgO-Al2O3 Ceramics Tested with Positron-Positronium Trapping Algorithm

“…Comparative analysis parameters of own positron trapping and corresponding parameters for modified matrix is shown in Table II. As was described in [18], the component with defectrelated τ int lifetime can reflect positron trapping sites caused by water. Under accepted prerequisites, these extended defects can be associated with pseudogap voids at the interface between the outer surface layer of agglomerated nanoparticles and innermost layer of surrounding initial matrix (as it well demonstrated in [24,25]).…”

“…This method is a test-indicator in terms of transformation of positronium sites in the initial MgO-Al 2 O 3 matrix towards positron trapping sites in MgO-Al 2 O 3 ceramics with absorbed water. In respect to algorithm described in [18], physical parameterization water-related sites can be finally performed taking (τ int , I int ) as corresponding components of the generalized twoterm decomposed PAL spectrum of a substance affected by embedded water immersion.…”

“…The effects caused by physical-adsorbed water in modified MgO-Al 2 O 3 ceramics were studied using the positron-positronium trapping algorithm detail described in [18] (in the case of three-component treatment of PAL spectra). This method is a test-indicator in terms of transformation of positronium sites in the initial MgO-Al 2 O 3 matrix towards positron trapping sites in MgO-Al 2 O 3 ceramics with absorbed water.…”

“…In this work, to clarify this feature, we shall analyze physical water-sorption process near grain boundaries in the modified MgO-Al 2 O 3 ceramics using positron-positronium trapping algorithm proposed in [18] (at interpretation of three-component treatment of PAL spectra) in comparison with chemical water-sorption process at decomposition of PAL spectra into four components.…”

Free‐volume nanostructural transformation in crystallized GeS2–Ga2S3–CsCl glasses

“…We also analyzed interface void volumes formed by nanocrystals using the x3-x2-decomposition procedure [16]. Transformations of the defect-related component of the positron annihilation lifetime spectra for crystallized 80GeSe 2 -20Ga 2 Se 3 chalcogenide glass confirmed the structural fragmentation of larger voids into smaller ones at the crystallization of GeGa 4 Se, Ga 2 Se 3 and GeSe 2 phases with further void agglomeration during the initial stage of annealing [15].…”