Synthesis and structural characterization of BaSr2Ge3O9

摘要

BaSr2Ge3O9 was prepared by high--temperature solid-state synthesis at 1100 degrees C in a platinum crucible from barium carbonate, strontium carbonate, and germanium(IV) oxide. The compound crystallizes in the triclinic space group P (1) over bar (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) angstrom, alpha = 83.0(2), beta = 77.0(2),. = 70.2(2)degrees, V = 464.3(6) angstrom(3), 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 eightfold coordinated.