Structure of glasses and composites in As<sub>2</sub>S<sub>3</sub>–Sb<sub>2</sub>S<sub>3</sub>–SbI<sub>3</sub> system

Abstract

Purpose. Composites on the basis x (As 2 S 3 ) y (Sb 2 S 3 ) z (SbI 3 ) glasses are suitable for creation of ferroelectric glassceramics, nonlinear dielectrics, memory media, elements for infrared and nonlinear optics, various sensors. This paper presents the results of thermal, X-ray diffraction and Raman studies of the conditions of formation and nature of crystalline inclusions in the glass matrix of the As 2 S 3 -Sb 2 S 3 -SbI 3 system during their thermal treatment. Methods. Differential thermal analysis (DTA), Raman and X-Ray diffraction spectroscopy. DTA curves were carried out in the temperature interval of 293–700 K. Heating rate was equal 3 K/min. Results. Danoheterogenous structure of glasses in As 2 S 3 -Sb 2 S 3 -SbI 3 system established on the basis of Raman spectra investigations. Their structural network is formed by only binary structural groups with heteropolar bonds (AsS 3/2 , SbS 3/2 , SbI 3 , AsI 3 ) and contains a certain amount molecular fragments with homopolar As-As and S-S bonds (As 4 S 4 , S 8 ). It has been established that the crystallization of glasses takes place in several stages. DTA curves of glasses recorded at 3 K/min revealed three exothermic effects. For example, for 40(As 2 S 3 )30(Sb 2 S 3 )30(SbI 3 ) glass temperatures maxima of these effects are equal 341, 398 and 530 K. The first and second effects are less pronounced due to nucleus formation and the formation of nanocrystals in glass matrix. The structure of the phase that arises in the glass matrix at annealing (348 and 398 K) corresponds to the structure of the crystalline SbSI. The formation of triple units SbS 2/2 I occurs as a result of the glass structural relaxation during its softening, which is accompanied by breaking and switching of homopolar and heteropolar chemical bonds in the binary groups that form the structural network of glasses. This process is accompanied by the diffusion of atoms in a distances of interatomic order. The sizes of antimony sulfoiodsde crystalline inclusions increase with annealing temperature and annealing time. The matrixes of the annealed As 2 S 3 -Sb 2 S 3 -SbI 3 system glasses, in which crystalline SbSI inclusions of different dimensions are formed, are determined mainly by As 4 S 4 structural groups linked together by fragments of chains or rings of sulfur atoms. Conclusions. DTA curves, X–ray powder diffraction patterns and Raman spectra of glasses in As 2 S 3 -Sb 2 S 3 -SbI 3 were investigated. The nanoheterogeneous structure of glasses was established. The crystallization of glasses takes place in several stages. The structure of the phase that arises in the glass matrix at annealing corresponds to the structure of crystalline antimony sulfoiodide. The sizes of SbSI crystalline inclusions are dependent on the heat treatment regimes.