Thermoanalytical properties and structure of (As2Se3)100−x(Sb2Se3)x glasses by Raman and 77Se MAS NMR using a multivariate curve resolution approach

Abstract

The basic thermoanalytical characteristics and structure of (As 2 Se 3) 100-x (Sb 2 Se 3) x bulk glasses over the whole glass-forming region (x = 0-50) were studied by DSC, StepScan DSC and both Raman and 77 Se MAS NMR spectroscopies. The glass transition temperature, T g , was found to increase only slightly from 184 to 190 °C with increasing Sb 2 Se 3 content, and the changes in the isobaric heat capacity at T g are also nearly compositionally independent. However, the isobaric heat capacity of glasses decreases 2 because of the higher atomic mass of antimony. The undercooled melts undergo crystallization when heated; As 2 Se 3 crystallizes for x  20, and both stoichiometric triselenides crystallize for higher x. 77 Se MAS NMR spectroscopy was used for the first time in the structural study of this pseudobinary system. The results of both NMR and Raman spectroscopies were combined, and their chemometric analysis was used to elucidate the structure of the glasses over the whole glass-forming region. It was concluded that the structure is based on randomly distributed AsSe 3/2 and SbSe 3/2 trigonal pyramids bridged by common selenium atoms and corresponds to the transition structure between a "random covalent network model" (RCNM) and a "chains crossing model" (CCM).

The influence of Sb on glass‐forming ability of Ga‐containing As2Se3 glasses

“…The maximum of Raman spectrum monotonically shifts with Sb addition from 229 cm −1 ( x =0) to 223 cm −1 ( x =0.04), 210 cm −1 ( x =0.12) and 203 cm ‐1 ( x =0.20) together with appearance of rapidly decreasing shoulder near ~230 cm −1 . These changes attest that some pyramidal AsSe 3/2 structural units interconnected by =As–Se–As= bridges are replaced by SbSe 3/2 pyramids interconnected by =Sb–Se–Sb= or =As–Se–Sb= bridges, whose vibrational modes are expected at lower energies (in agreement with the higher Sb weight) …”

“…In this work, partial As to Sb substitution within Ga y (As 0.40− x Sb x Se 0.60 ) 100− y cut‐section is studied to suppress this deleterious effect, thus enhancing the resultant glass‐forming ability with Ga addition. The Sb is known to be as isoelectronic analogue for valence electrons of As and is expected to be threefold coordinated and create trigonal SbSe 3/2 pyramidal units in Se‐based ChG . These structural units are easily linked with AsSe 3/2 pyramids without essential modification of glass properties (microhardness, glass‐transition temperature, etc.)…”

“…Thermal characteristics of Ga 2 (As 0.40− x Sb x Se 0.60 ) 98 ChG samples (see Table and Figure ) testify that onset value of glass‐transition temperature T g rises slightly with Sb addition. This behavior agrees well with the DSC results on (As 2 Se 3 )–(Sb 2 Se 3 ) ChG obtained by Cernoskova et al . Our DSC measurements show appearance of crystallization peak near 306°C in Sb‐rich Ga 2 (As 0.20 Sb 0.20 Se 0.60 ) 98 glass, whereas no crystallization peaks are observed in ChG with x =0.04 and 0.12 up to 350°C.…”

Ge-free chalcogenide glasses based on Ga-Sb-Se and their stabilization by iodine incorporation

“…Added to the glass, a shift of the vibrational peaks towards shorter wavenumber is expected in Raman measurement. First hypothesis consists in assuming the creation of new entities from GaSe4 A c c e p t e d m a n u s c r i p t [14,18,19] and SbSe3 [15][16][17][18] entities with substitutions of iodine like GaSe4-xIx (x = 0 to 3) or SbSe3xIx (x = 0 to 3). In contrast, atoms can change their coordination with the addition of iodine with, for instance, formation of GaI3 or Ga2I6 [19].…”

Nanoscale mechanism of rare‐earth doping in Ga‐codoped glassy As‐Sb selenides

“…It is known that partial As-by-Sb replacement within Ga y (As 0.40Àx Sb x Se 0.60 ) 100Ày cut-section reveals a stabilizing effect on ChG network suppressing parasitic crystallization processes caused by Ga addition. 27,28 That is why the Sbmodified As 2 Se 3 -based ChG will be examined, i.e., Gacodoped arsenic selenide g-Ga 2 (As 0.28 Sb 0.12 Se 0.60 ) 98 and g-Ga 2 (As 0.28 Sb 0.12 Se 0.60 ) 98 doped with 500 wppm of Pr 3+ .…”