Y(0.76)Ho(0.24)FeGe(2)O(7): a new member of thortveitite-like layered compounds

Y(0.76)Ho(0.24)FeGe(2)O(7) (yttrium holmium iron digermanate) was synthesized by solid-state reaction at 1573 K. This thortveitite-like compound presents a crystallographic group–subgroup isotranslational (klassengleiche) relation with some other pyrogermanates, such as FeInGe(2)O(7), In(1.08)Gd(0.92)Ge(2)O(7) and InYGe(2)O(7), which are configurationally isotypic with the Sc(2)Si(2)O(7) thortveitite structure first reported by Zachariasen [(1930 ▶). Z. Kristallogr. 73, 1–6]. Holmium cations share with yttrium the 4f Wyckoff position at the center of a seven-coordinated pentagonal bipyramid, while Fe atoms also occupy one site with Wyckoff position 4f at the center of the octahedron. All these sites have the point symmetry C (1). Two types of Ge(2)O(7) diorthogroups with point symmetry C (1h) are present in the structure, each one of them defining a layer type which alternates with the other. These diorthogroups have their tetrahedral groups in an eclipsed conformation.