Isothermal section at 900 °C of the Ce–Fe–Si ternary system

The phase equilibria in the ternary Ce–Fe–Si system at 900 °C was investigated by means of X-ray diffraction and Scanning Electron Microscope–Energy Dispersive X-ray Spectroscopy (SEM–EDS). A total number of six ternary compounds were characterized and the homogeneity ranges of the various ternary solid solutions of the binary boundary systems (Ce–Fe, Ce–Si and Fe–Si) were studied. A new ternary phase, CeFe13−ySiy (3.5 < y < 5) has been found. It crystallizes in the tetragonal space group I4/mcm (no. 140), with the cell parameters a = 7.892(1) Å and c = 11.666(1) Å for y = 4. Its crystal structure derives from the Ce2Ni17Si9-type, with fully ordered atoms on the crystallographic sites for CeFe9Si4. The phase diagram comprises four extensions of binaries into the ternary system, Ce2Fe17−xSix (0 < x < 3), CeFe2−xSix (0 < x < 0.15), CeFexSi2−α1−x (0 < x < 0.1) and CeFexSi2−α2−x (0 < x < 0.14), four ternary compounds CeFeSi2, CeFeSi, CeFe2Si2 and Ce5Fe2Si8, and two intermediate solid solutions CeFe13−xSix (2.4 < x < 2.6) and CeFe13−ySiy (3.5 < y < 5).