Crystal Structures and Reference Powder Patterns of BaR(2)ZnO(5) (R = La, Nd, Sm, Eu, Gd, Dy, Ho, Y, Er, and Tm)

Reference x-ray powder patterns and the crystal structures of the lanthanide compounds, BaR(2)ZnO(5), in which R = La, Nd, Sm, Eu, Gd, Dy, Ho, Y, Er, or Tm, were determined by the x-ray Rietveld refinement technique. A structural trend was confirmed for this series of compounds. The compounds with smaller ionic radii (R = Sm, Eu, Gd, Dy, Ho, Y, Er, or Tm) are isostructural to the orthorhombic “green phase” (BaY(2)CuO(5)). The lattice parameters for compounds with R = Tm to Sm range from a = 7.01855(9) Å to 7.20452(14) Å, b = 12.25445 (17) Å to 12.5882(2) Å, and c = 5.6786(14) Å to 5.81218(11) Å, respectively. R is sevenfold coordinated inside a monocapped trigonal prism. These prisms share edges to form wave-like chains parallel to the long b-axis. The BaR(2)ZnO(5) 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 BaLa(2)ZnO(5), and a = 6.75979(5) Å and c = 11.54560(12) Å for BaNd(2)ZnO(5). The structure consists of ZnO(4) tetrahedra (instead of planar CuO(4) groups as found in BaR(2)CuO(5)) with 10-fold coordinated bicapped square prismatic Ba and 8-fold coordinated bicapped trigonal prismatic R ions between them. The reference x-ray powder patterns will be submitted to the Powder Diffraction File (PDF).