Phase equilibria in the Cu2Se–SnSe–Sb2Se3 quasi-ternary system has been studied by differential thermal analysis and powder X-ray diffraction. Some polythermal sections, isothermal sections at 300 K of phase diagram projection liquidus surface are constructed. The regions primary crystallization phases, nature temperatures non- monovariant have determined. SnSe–CuSbSe2 quasi-binary section refi...