Abstract:'Cold' crystallization in 80GeSe2-20Ga2Se3 chalcogenide glass nanostructurized due to thermal annealing at 380°C for 10, 25, 50, 80, and 100 h are probed with X-ray diffraction, atomic force, and scanning electron microscopy, as well as positron annihilation spectroscopy performed in positron annihilation lifetime and Doppler broadening of annihilation line modes. It is shown that changes in defect-related component in the fit of experimental positron lifetime spectra for nanocrystallized glasses testify in fa… Show more
“…The PAL measurements were performed with the ORTEC instrument (using 22 Na source placed between two identical sandwiched samples) [ 7 , 22 ] at 22 °C and relative humidity RH = 35 % after drying, 7 days of water exposure (water vapor in a desiccator at RH = 100 %), and further final drying in a vacuum at 120 °C for 4 h. Each PAL spectrum was collected within a 6.15-ps channel width to analyze short and intermediate PAL components. To obtain data on longest-lived PAL components, the same ceramics were studied within a channel width of 61.5 ps [ 15 ].…”
The water-vapor sorption processes in nanoporous MgO-Al2O3 ceramics are studied with positron annihilation lifetime (PAL) spectroscopy employing positron trapping and positronium (Ps)-decaying modes. It is demonstrated that the longest-lived components in the four-term reconstructed PAL spectra with characteristic lifetimes near 2 and 60–70 ns can be, respectively, attributed to ortho-positronium (o-Ps) traps in nanopores with 0.3- and 1.5–1.8-nm radii. The first o-Ps decaying process includes “pick-off” annihilation in the “bubbles” of liquid water, while the second is based on o-Ps interaction with physisorbed water molecules at the walls of the pores. In addition, the water vapor modifies structural defects located at the grain boundaries in a vicinity of pores, this process being accompanied by void fragmentation during water adsorption and agglomeration during water desorption after drying.
“…The PAL measurements were performed with the ORTEC instrument (using 22 Na source placed between two identical sandwiched samples) [ 7 , 22 ] at 22 °C and relative humidity RH = 35 % after drying, 7 days of water exposure (water vapor in a desiccator at RH = 100 %), and further final drying in a vacuum at 120 °C for 4 h. Each PAL spectrum was collected within a 6.15-ps channel width to analyze short and intermediate PAL components. To obtain data on longest-lived PAL components, the same ceramics were studied within a channel width of 61.5 ps [ 15 ].…”
The water-vapor sorption processes in nanoporous MgO-Al2O3 ceramics are studied with positron annihilation lifetime (PAL) spectroscopy employing positron trapping and positronium (Ps)-decaying modes. It is demonstrated that the longest-lived components in the four-term reconstructed PAL spectra with characteristic lifetimes near 2 and 60–70 ns can be, respectively, attributed to ortho-positronium (o-Ps) traps in nanopores with 0.3- and 1.5–1.8-nm radii. The first o-Ps decaying process includes “pick-off” annihilation in the “bubbles” of liquid water, while the second is based on o-Ps interaction with physisorbed water molecules at the walls of the pores. In addition, the water vapor modifies structural defects located at the grain boundaries in a vicinity of pores, this process being accompanied by void fragmentation during water adsorption and agglomeration during water desorption after drying.
“…Such temperature shifts of vibrational frequencies can be caused by possible thermal expansion of the lattice [26] and nanovoid agglomeration. The fact of the nanovoid formation induced by CsCl additives in Ge-Ga-S has been definitely confirmed by positron annihilation lifetime spectroscopy [12, 15, 25, 27–29]. Fig.…”
Optical and FTIR spectroscopy was employed to study the properties of 80GeS2-20Ga2S3-CsCl chalcohalide glasses with CsCl additives in a temperature range of 77–293 K. It is shown that CsCl content results in the shift of fundamental absorption edge in the visible region. Vibrational bands in FTIR spectra of (80GeS2-20Ga2S3)100 − х(СsCl)x (x = 5, 10, and 15) are identified near 2500 cm−1, 3700 cm−1,, around 1580 cm−1, and a feature at 1100 cm−1. Low energy shifts of vibrational frequencies in glasses with a higher amount of CsCl can be caused by possible thermal expansion of the lattice and nanovoid agglomeration formed by CsCl additives in the inner structure of the Ge-Ga-S glass.
“…PAL results are fairly consistent with the DRAL studies presented in the form of correlations of S – W parameters ( Figure 5 ). All points on the dependence are grouped and located close to linear trajectory, which goes toward the direction of decreasing S and increasing W for non‐annealed 80GeSe 2 –20Ga 2 Se 3 glass and for the one annealed during 10 and 25 h. This behavior reflects a so‐called normal trend in changing of S – W parameters in the κ d – ρ correlation [ 42 ] and demonstrates the agglomeration of free‐volume defects in the initial stages of thermal annealing of glasses for 10 h with future fragmentation in ChG annealed at 25 h. At increase of annealing duration for 50 h, the evolution of S–W parameters changes to the opposite trend (abnormal tendency in the κ d – ρ correlation), which reflects the shrinkage defect‐related free volumes.…”
Herein, transformation of free‐volume extended defects in selected chalcogenide glasses caused by thermal annealing for 10, 25, and 50 h is studied. For 80GeSe2–20Ga2Se3 as well as for GeS2–Ga2S3 glasses with different GeS2 and Ga2S3 contents (80GeS2–20Ga2S3, 82GeS2–18Ga2S3, 84GeS2–16Ga2S3), positron annihilation lifetime spectroscopy and Doppler broadening of annihilation radiation methods are applied. By analyzing the positron annihilation lifetime spectra decomposed into two components, it is shown that the observed changes in the second defect‐related component for the 80GeSe2–20Ga2Se3 glasses confirm the agglomeration of free volumes in the initial stage of annealing (10 h) with further fragmentation (25 h) and shrinkage (50 h). Increased content of Ge‐related subsystem in the GeS2–Ga2S3‐based glasses results in the agglomeration of free‐volume defects in the 82GeS2–18Ga2S3 glasses with their further expansion in the 84GeS2–16Ga2S3 matrix.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
