Investigation of phase equilibria in the quaternary Ce-Mn-In-Ge system and isothermal sections of the boundary ternary systems at 800 °C

Highlights: • Ce-Mn-In, Mn-In-Ge, Ce-In-Ge, and Ce-Mn-Ge systems at 800 °C were examined. • Ce₃Mn₂Ge₃ and Ce₄₃Mn₁₈Ge₃₉ are new high-temperature phases with close composition. • Two new quaternary phases, Ce₄Mn₂InGe₄ and Ce₂Mn₂InGe₂, were discovered. - Abstract: Part of the quaternary Ce-Mn-In-Ge phase diagram has been examined through powder X-ray diffraction and energy-dispersive X-ray analysis. Two new quaternary (Ce₄Mn₂InGe₄ and Ce₂Mn₂InGe₂) and two ternary (Ce₃Mn₂Ge₃ and Ce₄₃Mn₁₈Ge₃₉) phases were found. The isothermal sections of the boundary ternary systems (Ce-Mn-In, Mn-In-Ge, Ce-In-Ge, and Ce-Mn-Ge) were determined at 800 °C. Among these, the Ce-Mn-Ge system deserves particular attention because the phase equilibria are complex. Relative to the previously reported phase diagram evaluated at a lower temperature (400 °C), three ternary phases (CeMn₂Ge₂, Ce₂MnGe₆, and CeMnGe) persist, Ce₂MnGe₅ does not form, and two new phases with very close composition (Ce₃Mn₂Ge₃ and Ce₄₃Mn₁₈Ge₃₉) appear at 800 °C. Ce₃Mn₂Ge₃ (orthorhombic Hf₃Ni₂Si₃-type) has a small homogeneity range (2%) deviating from the ideal composition, whereas Ce₄₃Mn₁₈Ge₃₉ (tetragonal La_2+xMnGe_2+y-type) has negligible homogeneity. Magnetic measurements on Ce₄Mn₂InGe₄ suggest ferromagnetic behaviour