The system Ho–Ni–In at 870 K

Abstract

The components interaction in the Ho–Ni–In system was investigated by X-ray powder diffraction and, partially, scanning electron microscopy with energy-dispersive X-ray spectroscopy. Isothermal section of the phase diagram was constructed in full concentration range at 870 K. The samples were synthesized in an arc-furnace on a water-cooled Cu-plate under an argon atmosphere and annealed in silica tubes at 870 K for 720 h. The phase analysis was performed by X-ray powder diffraction method. Twelve ternary compounds, namely HoNi 9 In 2 (YNi 9 In 2 -type structure), Ho 4 Ni 11 In 2 0 (U 4 Ni 11 Ga 2 0 -type structure), HoNi 4 In (MgCu 4 Sn-type structure), Ho 10 Ni 9 In 20 (Ho 10 Ni 9 In 20 -type structure), HoNi 1.0-0.5 In 1.0-1.5 (ZrNiAl-type structure), Ho 2 Ni 2 In (Mn 2 AlB 2 -type structure), Ho 2 Ni 1.8 In (Mo 2 FeB 2 -type structure), Ho 5 Ni 2 In 4 (Lu 5 Ni 2 In 4 -type structure), Ho 11 Ni 4 In 9 (Nd 11 Pd 4 In 9 -type structure), Ho 6 Ni 2 In (Ho 6 Co 2 Ga-type structure), ~ Ho 6 NiIn 2 (unknown structure) і Ho 13.35 Ni 3.17 In 3.48 (Lu 14 Co 3 In 3 -type structure) exist in the Ho–Ni–In system at the temperature of annealing. The substitution of Ni for In was observed for HoNi 1.00-0.50 In 1.00-1.50 compound. Besides, Ho can enter the structure of NiIn (CoSn-type structure) compound leading to formation of including subtraction type solid solution, which is stable up to 8 at. % Ho. The composition of this solid solution can be described by the formula Ho 0-0 . 08 NiIn 1-0 . 94 . The inclusion of holmium and indium atoms in position (2 e ) with the simultaneous exclusion of a small amount of indium atoms from position (1 a ) takes place in the homogeneity range of this solid solution. The character of interaction between the components in the ternary Ho–Ni–In system is similar to other related system R – T –In ( R – rare earth of the yttrium subgroup). The common feature of all these systems is the existence of large number isotypical ternary compounds, the formation of homogeneity range for compounds with ZrNiAl-type structure and including-subtraction type solid solutions based on the binary compound NiIn. Ke y words: holmium, indium, ternary compound, ternary system, isothermal section.