Phase Relationships of the Gd-Zn System

Abstract

Abstract The Gd-Zn system has been studied by performing differential thermal analysis (DTA) in closed crucibles, optical microscopy (OM), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and X-ray examination (XRD). Eight intermetallic phases were found: GdZn, cubic, cP2-CsCl type, congruent melting at 1020 °C, GdZn2, orthorhombic, oI12-CeCu2 type, congruent melting at 1010 °C, GdZn3, orthorhombic, oP16-YZn3 type, peritectic decomposition at 905 °C, Gd3Zn11, orthorhombic, oI28-La3Al11 type, peritectic decomposition at 880 °C, Gd13Zn58, hexagonal, hP142-Gd13Zn58 type, melting point at 920 °C, Gd3Zn22, tetragonal, tI100-Pu3Zn22 type, peritectic decomposition at about 910 °C, Gd2Zn17, high temperature (H.T.) form, rhombohedral, hR57-Th2Zn17 type and low temperature (L.T.) form, hexagonal, hP38-Th2Ni17 type, congruent melting at 935 °C and GdZn12 tetragonal, tI26-ThMn12 type, peritectic decomposition at 660 °C. Five eutectic reactions occur at 780 °C and 27 at% Zn ((αGd) + GdZn), at 945 °C and 59 at% Zn (GdZn + GdZn2), at 875 °C and 77 at% Zn (GdZn3 + Gd3Zn11), at 885 °C and 84 at% Zn (Gd13Zn58 + Gd3Zn22) and finally at 400 °C and 99.5 at% Zn (GdZn12 + (Zn)). A catatectic equilibrium was found in the Gd-rich end. The results are discussed and compared with those for the other rare earthzinc (R-Zn) systems. A brief outline of the general alloying behaviour of the 12th group elements (Zn, Cd and Hg) with the rare earth metals is also presented.