Structures and phase equilibria in the ternary Cu-As-Sb system

The PhD focus on the determination of the ternary Cu-As-Sb phase diagram in the copperrich corner of the system (64-100 at.% Cu). There are no works carried out on the Cu-As-Sb system yet; only the respective binary systems were studied [1-6]. The starting goal was to carry out not only the study of one isothermal section (i.e.: at 500 ºC or 600 ºC), but (and more ambitiously) to perform an investigation also as a function of temperature. This system is of particular importance for extractive metallurgy as copper mined from sulfosalt minerals, such as tetrahedrite, tennantite, and enargite (all so-called Fahlores), which are characterized by high concentrations of arsenic (As) and antimony (Sb). After starting the experimental work on the ternary Cu-As-Sb system, it became soon clear that the planned analyses would not have provided sufficient insight into the study of this system: it was quickly noted that some data reported for the Cu-As diagram were unreliably and the system was still lacking of fundamental data that were and are essential for the interpretation of results from the work on the ternary Cu-As-Sb system. Consequently, it has been decided to study formation, crystal structure and polymorphism of intermetallics of the Cu-As system (mostly Cu3As and Cu5As2; both reported dimorphic, each one with a low- and high-temperature structure). Then, it was also planned to possibly perform further and deeper analyses as crystal structure determinations and physical properties measurements. It is the aim of the PhD-research to: - Study the alloys in as-cast and annealed condition to understand phase formation, stability, the crystallo-chemical changes and transitions resulting from thermal treatments; - Determine the copper-rich corner of the Cu-As-Sb phase diagrams (64-100 at.% Cu); - Identify new phases and ternary compounds yet unknown, study their thermodynamic stability and crystal structure(s). - Plan (future) specific physical properties measurements, in view of identifying desirable and exploitable properties of either the binary or ternary compounds.