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The antimony-rich iridium antimony phase diagram was investigated by means of differential thermal analysis, microprobe analysis, metallography and X-ray powder diffractions.
IrSb is Molybdenum Carbide MAX Phase-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ir3+ is bonded to six equivalent Sb3- atoms to form a mixture of corner, edge, and face-sharing IrSb6 octahedra. The corner-sharing octahedral tilt angles are 51°. All Ir–Sb bond lengths are 2.73 Å. Sb3- is bonded in a 6-coordinate geometry to six equivalent Ir3+ atoms.
IrSb3 is Skutterudite structured and crystallizes in the cubic Im-3 space group. The structure is three-dimensional. Ir3+ is bonded to six equivalent Sb1- atoms to form corner-sharing IrSb6 octahedra. The corner-sharing octahedral tilt angles are 55°. All Ir–Sb bond lengths are 2.65 Å. Sb1- is bonded in a 2-coordinate geometry to two equivalent Ir3+ and two equivalent Sb1- atoms. There are one shorter (2.89 Å) and one longer (3.01 Å) Sb–Sb bond lengths.
IrSb2 is Marcasite-like structured and crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Ir5+ is bonded to six Sb+2.50- atoms to form a mixture of edge and corner-sharing IrSb6 octahedra. The corner-sharing octahedra tilt angles range from 51–58°. There are a spread of Ir–Sb bond distances ranging from 2.63–2.72 Å. There are two inequivalent Sb+2.50- sites. In the first Sb+2.50- site, Sb+2.50- is bonded in a 4-coordinate geometry to three equivalent Ir5+ and one Sb+2.50- atom. The Sb–Sb bond length is 2.89 Å. In the second Sb+2.50- site, Sb+2.50- is bonded in a 4-coordinate geometry to three equivalent Ir5+ and one Sb+2.50- atom.