INVESTIGATION OF GLASS FORMATION AND PHYSICO-CHEMICAL PROPERTIES OBTAINED PHASES IN THE SYSTEM As2Te3-TlS

Using methods of physicochemical analysis: differential thermal analysis (DTA), X-ray diffraction analysis (XRD), microstructural analysis (MSA), as well as determination of microhardness and density, the As2Te3-TlS system was studied and a T-x phase diagram was constructed. The phase diagram of the As2Te3-TlS system belongs to the partially quasi-binary eutectic type and is characterized by the formation of a new quaternary compound TlAs2STe3 and Tl3As2S3Te3. The compounds TlAs2STe3 and Tl3As2S3Te3 melt congruently at 270°C and 240°C, respectively. X-ray diffraction analysis showed that the compound TlAs2STe3 crystallizes in a tetragonal syngony with lattice parameters: a=10.70; с=9.28 Å, z=4, density ρpucn/=7.10 g/cm3, ρX-ray= 7.12 g/cm3. Tl3As2S3Te3 crystallizes in a hexagonal syngony with lattice parameters: a = 11.54; с=9.58 Å, z=4, density ρpucn/=7.28 g/cm3, ρX-ray= 7.37 g/cm3. In the As2Te3-TlS system, solid solutions based on the As2Te3 compound reach -3.5 mol % TlS, and solid solutions based on TlS are practically not established. In the system, the compounds As2Te3 and TlAs2STe3 form a eutectic with a composition of 35 mol % TlS at melting point 180°C. Another eutectic is formed between TlAs2STe3 and Tl3As2S3Te3, composition 67 mol % TlS, temperature 165°C. Under normal conditions, the compounds TlAs2STe3 and Tl3As2S3Te3 are obtained in a glassy state and participate in the system as glass formers. Thus, in the As2Te3-TlS system upon slow cooling, the glass transition region extends to the region of 45-85 mol % TlS. In the quenching mode in liquid nitrogen, it was possible to obtain glassy alloys from 85 to 100 mol % TlS