Solid solubility metastable extension of rare earth metals in gold

Abstract

Metastable extended solid solubility of rare earth (RE) metals in gold was studied by measuring the lattice parameters of solid solutions of rapidly solidified Au-RE alloys using X-ray diffraction. The cooling rate used for the preparation of the alloys was about 106 K/s. It was found that the metastable solid solubilities of Ce, Sm, Gd, Dy, Er, Yb and Y in gold were 0.3, 0.4, 1.5, 9.0, 13, 13.4 and 10 atrespectively. The solid solubilities of RE metals in gold increased with decreasing relative difference of atomic radius between the RE metal and gold. The extended solid solubilities of RE metals in Au, Ag, and Cu were compared. The relatively large solid solubility in gold is explained in terms of electron transfer from the RE atoms to gold atoms. Under the conditions of rapid solidification, the Au-RE alloys tended to form amorphous alloys more readily than do Ag-RE alloys.