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 (As2Se3)100−x(Sb2Se3)x bulk glasses over the whole glass-forming region (x=0–50) were studied by DSC, StepScan DSC and both Raman and 77Se MAS NMR spectroscopies. The glass transition temperature, Tg, was found to increase only slightly from 184 to 190°C with increasing Sb2Se3 content, and the changes in the isobaric heat capacity at Tg are also nearly compositionally independent. However, the isobaric heat capacity of glasses decreases because of the higher atomic mass of antimony. The undercooled melts undergo crystallization when heated; As2Se3 crystallizes for x≤20, and both stoichiometric triselenides crystallize for higher x.77Se 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 AsSe3/2 and SbSe3/2 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).