Phase equilibrium and glass formation between AsS and ErS compounds were studied by methods of physicochemical analysis: differential-thermal (DTA), X-ray phase (XRD), microstructural analysis (MSA), as well as by measuring microhardness and density. The T-x phase diagram of the AsS–ErS system was constructed. It has been established that the phase diagram of the AsS–ErS system is quasi-binary, of the eutectic type and is characterized by the formation of the chemical compound ErAsS₂. The ErAsS₂ compound is formed as a result of the peritectic reaction M+ErS↔ ErAsS₂ at 750⁰C and crystallizes in the tetragonal syngony with lattice parameters: a=13.62; c=18.93 Ǻ; ρ_puc= 5.17 g/cm³, ρ_X-ray= 5.21 g/cm³. The eutectic composition between the AsS and ErS compounds is 10 mol % ErS and a temperature of 280^oC. Under normal cooling conditions, the area of glass formation based on AsS reaches 10 mol % ErS. For glass alloys, some physicochemical properties have been studied. Solubility based on AsS reaches up to 1.5 mol % ErS, and based on ErS, the solubility is practically not established

doi.org/10.32737/0005-2531-2022-2-87-92