Erbium-rich region of the ternary Er-Ni-Sb system: Solid state phase equilibria at 1073K 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 1073K 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=0.070. 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 1073K in the ternary phase Er5Sb3-xNix tends to stabilize the β-Yb5Sb3 type