Pb 1.32 V 8.35 O 16.7 and PbV 6 O 11 . The former adopts a hollandite-related structure with lead atoms and VO 4 tetra-The crystal structure of Ba 2 V 3 O 9 has been determined and refined to final R and R w values of 0.025 and 0.028 from 1562 hedra occupying the large tunnels of the V 8 O 16 hollandite independent single crystal reflections. It crystallizes in the space framework. The structure of the latter is closely related group P2 1 /m with a โซุโฌ 9.302(1) A ห, b โซุโฌ 5.969(1) A ห, c โซุโฌ 8.118(1) A ห, to that of AV 6 O 11 compounds (A ฯญ Na, Sr) which and โค โซุโฌ 113.96 (1)ุ. The structure consists of one-dimensional crystallize with an R-type hexagonal ferrite structure rutile-type chains of edge-sharing VO 6 octahedra parallel to (2-4). A solid solution phase BaV 10ฯชx O 17 (0.10 ี
x ี
the b axis. The VO 4 tetrahedra share corners with VO 6 octahedra 0.65) has been described that also displays a modified of a single rutile-type chain to form one-dimensional [V 3 O 9 ] 4ุ ุ hollandite structure whose tunnels accommodate altercolumns which are held together by Ba 2ุ ions. In this mixed nately Ba and O atoms. The tunnel O atoms generate valence compound V 4ุ and V 5ุ ions are distributed in an oroctahedral sites which are statistically occupied by V dered way in octahedra and tetrahedra, respectively. In the atoms, thus causing the wide solid-solution range (5). almost perfect O 6 octahedron the vanadium atom is off-center Bouloux et al. (6) have reported a hollandite-type phase so that it forms a short vanadyl VuO bond of 1.686(3) A ห, typical Ba x V 8 O 16 , (1.20 ี
x ี
1.36), and very recently Kanke of a V 4ุ ion. This compound is a barium vanadyl vanadate et al. (7) refined the crystal structure of the tetragonal Ba 2 (VO)(VO 4 ) 2 . It is the first example of isolated rutile-type chains found with V 4ุ ions.
Magnetic susceptibility measure-priderite-type compound Ba 1.09 V 8 O 16 . These phases conments show that this phase is an antiferromagnet with T N ะฅ tain both trivalent and tetravalent vanadium cations. The 58 K. At about 20 K magnetic anisotropy causes a canted spin recently described Ba 8 V 7 O 22 is the first example of a arrangement.