The structure was refined by using a combination of X-ray and high-resolution neutron powder diffraction. Iterative simulation of 27Al nuclear magnetic resonance data confirmed the presence of two Al sites in an approximately 1:1 ratio. One of these was octahedral and the other was tetrahedral. The structure was refined anisotropically in the orthorhombic space-group: Pbam, a = 0.77134, b = 0.81139, c = 0.56914nm, Z = 2. The structure consisted of edge-sharing columns of AlO6 octahedra which ran parallel to the c-axis. The columns were linked by pairs of apex-sharing AlO4 tetrahedra, with Bi atoms located between the columns. The Bi 6s2 lone pairs pointed towards vacant sites in the structure. A 1-dimensional conductivity mechanism along the c-axis vector was proposed which involved those sites.

Structure and Oxide Ion Conductivity Mechanism in Bi2Al4O9 by Combined X-Ray and High-Resolution Neutron Powder Diffraction and 27Al Solid State NMR. I.Abrahams, A.J.Bush, G.E.Hawkes, T.Nunes: Journal of Solid State Chemistry, 1999, 147[2], 631-6