Structure of Bi2Nd4O9 Monoclinic Phase

A new phase, Bi2Nd4O9, was synthesized in the binary system Bi2O3–Nd2O3 and structurally characterized from powder X-ray diffraction data. It crystallizes in monoclinic symmetry with lattice parameters a=6.7037(2) Å, b=3.9062(1) Å, c=3.9542(1) Å, β=125.258(1)°, Z=2, and a subcell space group of C2/m. Its average structure had been determined by X-ray powder diffraction and refined by the Rietveld method. The average structure can be described as an oxygen-deficient fluorite structure of the δ-Bi2O3 type with Nd and Bi randomly distributed on the cation site, similar to Bi2La4O9 reported by Chen et al. (J. Solid State Chem. 124, 300 (1996)). In addition, a strong superstructure had been observed by transmission electron microscopy.