PHASE EQUILIBRIUM IN THE Cu2Se – CdSe – Sb2Se3 QUASITERNARY SYSTEM

Abstract

Based on the results of studying the synthesized samples by X-ray phase analysis, the isothermal section of the Cu2Se – CdSe – Sb2Se3 system at 620 K has been constructed. There are five quasiternary systems, which divide the system on the five fields of the three-phase equilibrium: CuSbSe2 – CdSe – Sb2Se3; CuSbSe2 – CdSe – Cu12CdSb4Se13; Cu2Se – CdSe – Cu12CdSb4Se13; Cu2Se – Cu3SbSe3 – Cu12CdSb4Se13; Cu3SbSe3 – Cu12CdSb4Se13 – CuSbSe2. In the system, the existence of a new quaternary compound Cu12CdSb4Se13, which crystallizes in cubic syngony, Sp.Gr. I-43m, a = 1.06945 (1) nm, of tetrahedrite structural type. Based on the results of the differential thermal and X-ray phase analyzes of the synthesized samples, four polythermal sections have been constructed. One phase diagram of the CdSe – CuSbSe2 system has been built, which is a triangulating section of the quasiternary system. It divides the investigated system on two subsystems: Cu2Se – CdSe – CuSbSe2 and CuSbSe2 – CdSe – Sb2Se3. It has been found that the CdSe – CuSbSe2 phase diagram is a system of eutectic type with coordinates of eutectic point 15 mol % CdSe, Te3 = 710 K. The solubility based on the initial components is insignificant and at 620 K, the annealing temperature, is reduced to a minimum. The nature of the formation of the tetrahedral compound Cu12CdSb4Se13 from the peritectic reaction L p2+ Cu2Se ↔ Cu12CdSb4Se13 at 750 K has been investigated. The liquidus surface projection of the quasi-ternary system Cu2Se – CdSe – Sb2Se3 onto the concentration triangle has been built using the obtained results and literature data. The liquidus surface consists of the fields of primary crystallization of the phases: Cu2Se, CdSe, Sb2Se3, Cu3SbSe3, Cu12CdSb4Se13 and CuSbSe2. The largest area is occupied by the primary crystallization field of the binary CdSe compound. The nature, temperatures, and coordinates of non- and monovariant equilibria have been also established.

Keywords

• квазіпотрійна система
• фазові рівноваги
• ізотермічний переріз
• проекція поверхні ліквідусу