Erbium-rich region of the ternary Er–Ni–Sb system: Solid state phase equilibria at 1073 K and crystal structures of the new ternary compound Er5Sb3−xNix (x = 0.48) and both modifications of Er5Sb3

The solid state phase equilibria in the Er-rich region of the ternary Er–Ni–Sb system were determined at 1073 K using experimental techniques such as X-ray diffraction, scanning electron microscopy and electron probe microanalysis. In addition to the ternary phase Er5Ni2Sb previously reported, a new phase Er5Sb3−xNix (x = 0.48) was obtained, the structure of which was solved from X-ray single crystal data: space group Pnma, a = 1.17522(3) nm, b = 0.90437(3) nm, c = 0.79144(5) nm, R1 = 0.067, wR2=0.070wR2=0.070. Moreover, for the first time, both modifications of the binary antimonide Er5Sb3 were obtained and their structures were studied from X-ray powder diffraction data. The low-temperature form belongs to the Mn5Si3 type: space group P63/mcm, a = 0.88062(4) nm, c = 0.62139(9) nm, RI = 0.074, Rp = 0.150, while the high-temperature form exhibits the β-Yb5Sb3 type: space group Pnma, a = 1.16897(3) nm, b = 0.91425(3) nm, c = 0.80217(2) nm, RI = 0.077, Rp = 0.125. According to these results, one can conclude that the substitution of antimony by nickel at 1073 K in the ternary phase Er5Sb3−xNix tends to stabilize the β-Yb5Sb3 type.