Preparation and Crystal Structure Analysis of Ba2BiGa11O20

Abstract

X-ray structure investigations of ternary BaO–Ga2O3crystals grown in a Bi2O3flux led to discovery of a quaternary compound of ideal composition Ba2BiGa11O20. Single-crystal X-ray diffraction indicates a monoclinic unit cell with parametersa=14.9283(14) Å,b=11.7046(8) Å,c=5.1170(5) Å, andβ=91.137(7)°. The structure is similar to that of Ba3TiAl10O20and related compounds. Three different refinement trials were completed, involving different treatments of positioning of bismuth or gallium atoms shifted from normal barium and gallium sites. The refinement selected as representing the best model has only one bismuth atom positioned near a barium site at a displacement of 0.495 Å. A crystal chemical analysis based on the X-ray data suggests that the displacement of bismuth atoms is due to the stereochemical activity of the 6s2lone pair. X-ray refinement was carried out by full-matrix least squares onF2on all data, to giveR1=0.0689 andwR2=0.1802 for 104 parameters and 1361 independent reflections. The final position assignments were analyzed via bond valence sum calculations. Other crystal data:M=1570.58, space groupI2/m(No. 12),V=893.92(14) Å3,Z=2,Dc=5.835 g cm−3, MoKα=0.71073 Å,μ=30.506 mm−1, 2θmax=59.98°.