Crystal Structure of BaV13O18

Single crystals of BaV13O18 (V+2.62) containing a small amount of Cr (about 7% of vanadium sites) were prepared by heating a mixture of BaCO3, V2O5, V, and Cr powders at 1973 K for 40 h in flowing Ar. Crystal structure analysis using single-crystal data (Rigaku AFC7R, 4037 reflections) showed that the BaV13O18 has a rhombohedral unit cell with ah=12.621(5) ?, ch= 7.020(5) ?, V=968.4(9) ?3, Z=3, Dcal=5.595 g·cm-3, and space group R-3 (R1=1.96%, wR2=3.60%, S=1.095). In the structure, Ba and O formed a cubic close-packed arrangement and every V was coordinated by six O. BaV13O18 has three kinds of vanadium environments: one almost regular octahedral site and two distorted octahedral sites. VO6 octahedra share their corners and edges.