Structure and Oxidation States of Giant Unit Cell Compound Dy117+xFe57–ySn112–z

Motivated by the complex structure and properties of giant unit cell intermetallic compounds, a new isostructural Fe analogue of the Dy117Co57Sn112 structure type was synthesized. Single crystals of Dy122Fe55Sn101 were grown at 1260 °C via a Dy–Fe eutectoid flux. The Fe analogue also adopts the space group Fm3m with lattice parameters a = 29.914(9) A, V = 26769(23) A3, and Z = 4. Dy122Fe55Sn101 has a large cell volume, structural complexity, and consists of seven Dy, eight Fe, and ten Sn unique crystallographic sites. There are fifteen fully occupied atomic positions, three unique pairs of alternating atomic positions with positional disorder, and seven partially occupied atomic sites. Within this complex unit cell, only approximately half the unique atomic positions are fully occupied with the remainder of the atoms either positionally or occupationally disordered. X-ray photoelectron spectroscopy indicates that the compound contains Dy3+, Fe0, Fe2+, Sn0, and Sn4+.