AbstractBaSr2Ge3O9 was prepared by high-temperature solid-state synthesis at 1100°C in a platinum crucible from barium carbonate, strontium carbonate, and germanium(IV) oxide. The compound crystallizes in the triclinic space group P1̅ (no. 2) isotypically to walstromite BaCa2Si3O9. The structure was refined from single-crystal X-ray diffraction data: a=7.104(5), b=10.060(7), c=7.099(5) Å, α=83.0(2), β=77.0(2), γ=70.2(2)°, V=464.3(6) Å3, R1=0.0230, and wR2=0.0602 for all data. BaSr2Ge3O9 is characterized by three-membered rings of germanate tetrahedra. There are three crystallographically different Ge sites (Ge1, Ge2, and Ge3) in each [Ge3O9]6− ring. The rings occur in layers with the apices of alternating rings pointing in opposite directions. The Sr2+ and Ba2+ ions are located in between. The Sr1 cation is eight-fold coordinated, while Sr2 is octahedrally surrounded by oxide anions, and the Ba cation again eight-fold coordinated.
Structural Characterization of Caddisfly Silk with Solid-State NMR and X-Ray Diffraction