Solid-state phase equilibria in the Er-Nd-Fe ternary system at 1073 K

Abstract

The solid state phase equilibria in the ternary Er-Nd-Fe system at 1073 K in all the composition ranges were investigated using the experimental results of the X-ray powder diffraction analysis (XRD) as well as those obtained from the Scanning electron microscopy (SEM) equipped with Energy dispersive spectroscopy (EDS). The binary systems Er–Fe, Er–Nd and Nd-Fe were investigated prior to the study of the ternary one. Six binary compounds were identified to exist at this isothermal sectionss at 1073 K namely: ErFe2 (Fd3¯m-MgCu2 structure type), ErFe3 (R3¯m-PuNi3 structure type), Er6Fe23 (Fm-3m-Th6Mn23 structure type), Er2Fe17 (P63/mmc-Th2Ni17 structure type), Nd2Fe17 (R3¯m-Th2Zn17 structure type), and δ-NdEr (R3¯m-Sm structure type). No new ternary compounds were found in all investigated ternary alloy samples. The phase relations are governed by seven three-phase regions, sixteen two-phase regions and nine single-phase regions, as well as a small liquid area in the Nd-rich region. At 1073 K, we have observed that the highest solubility of Nd in ErFe2 is about 16.6 at. % Nd, while the Er1−xNdxFe3 solid solution based on binary ErFe3 extends up to 7.5 at. % Nd. The XRD and the SEM/EDS analyses show that there is no miscibility of Nd in Er6Fe23. The pair of the binary compounds Er2Fe17 and Nd2Fe17 extend through the ternary system parallel to the Nd-Er edge. The maximum homogeneity range of the Er2−xNdxFe17 solid solution reaches 5.3 at. % Nd, while that of the Nd2−xErxFe17 solid solution is about 1.6 at. % Er. In the Er-Nd binary system, the maximum solid solubility of Nd in Er is about 38.4 at. % Nd, and the solubility limit of Er in Nd is about 29.8 at. % Er.