Crystal Structures and Reference Powder Patterns of BaR2ZnO5 (R = La, Nd, Sm, Eu, Gd, Dy, Ho, Y, Er, and Tm)

Reference x-ray powder patterns and the crystal structures of the lanthanide com-determined by the x-ray Rietveld refinement technique. A structural trend was confirmed for this series of compounds. The compounds with smaller ionic radii are isostructural to the orthorhombic " green phase " (BaY2CuO5). The lattice parameters for compounds with R = Tm to Sm range from R is seven-fold coordinated inside a monocapped trig-onal prism. These prisms share edges to form wave-like chains parallel to the long b-axis. The BaR2ZnO5 compounds which contain larger size R (La and Nd) crystallize in the tetragonal space group I4/mcm. The lattice parameters are a = 6.90982(10) and c = 11.5977(2) Å for BaLa2ZnO5, and a = 6.75979(5) Å and c = 11.54560(12) Å for BaNd2ZnO5. The structure consists of ZnO4 tetrahedra (instead of planar CuO4 groups as found in BaR2CuO5) with 10-fold coordinated bicapped square prismatic Ba and 8-fold coordinated bicapped trig-onal prismatic R ions between them. The reference x-ray powder patterns will be submitted to the Powder Diffraction File (PDF).