Crystal structure of Bi2W2O9, the n=2 member of the homologous series (Bi2O2)BVInO3n+1 of cation-deficient Aurivillius phases

The crystal structure of Bi 2 W 2 O 9 has been solved by single crystal X-ray diffraction data analysis and refined to R=0.046 for 991 independent reflections. Bi 2 W 2 O 9 crystallizes with orthorhombic symmetry, Pna2 1 space group, Z=4, a=5.440(1), b=5.413(1), c=23.740(5) Å. The model previously proposed by Watanabe et al., i.e. Bi 2 O 2 layers interleaved with ReO 3 -like slabs of W 2 O 7 , has been confirmed. The distortion of the W 2 O 7 octahedral network has been analysed and compared to that observed in homologous Aurivillius phases.