Synthesis and crystal structure of Gd2TeO6

The new oxotellurate(VI) Gd2TeO6 was synthesized by solid-state reaction of equimolar mixtures of Gd2O3 and TeO3 in evacuated silica tubes at 800 deg. C within 10 days. This compound crystallizes in the orthorhombic system with the space group P212121 (no. 19) and the lattice constants a=532.52(4), b=916.03(8), c=1004.60(9) pm (Z=4). The crystal structure was determined by X-ray single-crystal diffraction techniques and refined with R1=0.028, wR2=0.059 and a Flack-x parameter of -0.002(2) for 2157 unique reflections. In the La2TeO6-type crystal structure of Gd2TeO6, the Gd3+ cations occupy two of the nine independent atomic positions and are coordinated sevenfold by oxygen. Separately from each other, both coordination polyhedra [GdO7] build zigzag chains along [100] via common edges (Gd1) and corners (Gd2), respectively. Each of the chains order as hexagonal rod packing. Finally, both of them combine by linkage via edges and corners again to form a complex 3∞{[GdO3]3-} framework. The isolated [TeO6]6- octahedra reside in the oval channels of this arrangement