Y0.76Ho0.24FeGe2O7: 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.