Phase relationships of the Gd-Zn system

The Gd-Zn system has been studied by performing differential thermal analys is (DTA) in closed crucibles, optical microscopy (OM), scanning electron mi croscopy (SEM), electron probe microanalysis (EPMA), and X-ray examination (XRD). Eight intermetallic phases were found: GdZn, cubic, cP2-CsCl type, c ongruent melting at 1020 degreesC, GdZn2, orthorhombic, oI12-CeCu2 type, co ngruent melting at 1010 degreesC, GdZn3, orthorhombic, oP16-YZn3 type, peri tectic decomposition at 905 degreesC, Gd3Zn11, orthorhombic, oI28-La3Al11 t ype, peritectic decomposition at 880 degreesC, Gd13Zn58, hexagonal, hP142-G d13Zn58 type, melting point at 920 degreesC, Gd3Zn22, tetragonal tI100-Pu3Z n22 type, peritectic decomposition at about 910 degreesC, Gd2Zn17, high tem perature (H. T.) form, rhombohedral, hR57-Th2Zn17 type and low temperature (L. T.) form, hexagonal, hP38-Th2Ni17 type, congruent melting at 935 degree sC and GdZn12 tetragonal, tI26-ThMn12 type, peritectic decomposition at 660 degreesC. Five eutectic reactions occur at 780 degreesC and 27 at% Zn ((al pha Gd)+ GdZn), at 945 degreesC and 59 at% Zn (GdZn + GdZn2), at 875 degree sC and 77 at% Zn (GdZn3 + Gd3Zn11), at 885 degreesC and 84 at% Zn (Gd13Zn58 + Gd3Zn22) and finally at 400 degreesC and 99.5 at% Zn (GdZn12 + (Zn)). A catatectic equilibrium was found in the Gd-rich end. The results are discus sed and compared with those for the other rare earth-zinc (R-Zn) systems. A brief outline of the general alloying behaviour of the 12(th) group elemen ts (Zn, Cd and Hg) with the rare earth metals is also presented.