Structure and Oxide Ion Conductivity Mechanism in Bi2Al4O9 by Combined X-Ray and High-Resolution Neutron Powder Diffraction and 27Al Solid State NMR
✍ Scribed by I. Abrahams; A.J. Bush; G.E. Hawkes; T. Nunes
- Publisher
- Elsevier Science
- Year
- 1999
- Tongue
- English
- Weight
- 217 KB
- Volume
- 147
- Category
- Article
- ISSN
- 0022-4596
No coin nor oath required. For personal study only.
✦ Synopsis
The structure of Bi 2 Al 4 O 9 has been re5ned using a combination of X-ray and high-resolution neutron powder di4raction. Iterative simulation of the 27 Al MAS solid state NMR data con5rms the presence of two Al sites, one octahedral and one tetrahedral, in an approximate 1:1 ratio. The structure of Bi 2 Al 4 O 9 has been re5ned anisotropically in the orthorhombic space group Pbam, with a ؍ 7.7134(1), b ؍ 8.1139(2), c ؍ 5.6914(1) A s , and Z ؍ 2. The re5nement terminated with R wp ؍ 17.09% (X ray), 11.44% (neutron); R ex %25.4؍ (X ray), 3.22% (neutron). The structure consists of edge-sharing columns of AlO 6 octahedra running parallel to the c-axis. These columns are linked by pairs of apex sharing AlO 4 tetrahedra, with Bi atoms located between the columns. The Bi 6s 2 lone pairs point toward vacant sites in the structure. A one-dimensional conductivity mechanism along the c-axis vector is proposed involving these sites.