Experimental determination of the phase relations in the Mn–As–Pr ternary system at 700 °C

Highlights: • The isothermal section of the Mn–As–Pr system at 700 °C is established. • The formation of new ternary phase Ω with a composition Mn₁₆As₂₅Pr₉ is determined. • The maximum solubilities of Pr in MnAs and Mn in AsPr are determined. Isothermal section at 700 °C of the ternary Mn–As–Pr system was established by means of X-ray diffraction, scanning electron microscopy and energy dispersion spectroscopy techniques. This isothermal section consists of 11 single-phase, 20 two-phase regions, and 10 three-phase regions. The maximum solubility of Pr in MnAs is less than 1.25 at.%Pr and that of Mn in AsPr is less than 3 at.%Mn. The phase Mn₄As₃ does not exist under the applied experimental conditions. An existence of a new ternary phase Ω is observed in the Mn–As–Pr system at 700 °C. Since all the attempts to prepare a single ternary phase (Ω) sample were unsuccessful, the structure of phase Ω has not been solved and its chemical composition is approximately defined as Mn₁₆As₂₅Pr₉ from the SEM-EDS analyses.