A study of structures and properties in perovskite-related oxide compounds

The single crystal structure of the {dollar}rm (Pbsb{lcub}0.71{rcub}Cusb{lcub}0.29{rcub})Srsb 2(Ysb{lcub}0.73{rcub}Casb{lcub}0.27{rcub})Cusb 2Osb7{dollar} phase was determined. The tetragonal lattice constants are a = 3.8207(4)A, c = 11.826(1)A, space group P4/mmm, and R = 0.0269 for 179 observed reflections. The structure can be described as consisting of CuO{dollar}sb2{dollar}-(Y,Ca)-CuO{dollar}sb2{dollar} layers with PbO{dollar}sb6{dollar} octahedra flanking the layers and Sr in the oxygen interstice. This compound is semiconducting and shows no superconducting transition.; An oxygen deficient ordered perovskite phase {dollar}rm (Lasb{lcub}6.16{rcub}Srsb{lcub}1.84{rcub})Cusb{lcub}7.66{rcub}Osb{lcub}20{rcub}{dollar} was analyzed by single crystal x-ray diffraction. The tetragonal space group is P4/mbm, a = 10.7468(8)A, c = 3.8633(3)A, and R = 0.032 for 385 observed reflections. The structure is formed by the articulation of Cu octahedra, square pyramids, and square coplanar nets into a three dimensional frame work. La/Sr are in 10-fold coordination to oxygen atoms in a perovskite-like arrangement. This compound shows metallic conductivity.; The single crystal structure of {dollar}rm (Casb{lcub}0.82{rcub}Prsb{lcub}0.18{rcub})sb2(Cosb{lcub}0.83{rcub}Alsb{lcub}0.17{rcub})sb2Osb5{dollar} phase with brownmillerite structure was determined. The orthorhombic lattice constants are a = 5.2789(5)A, b = 14.998(2)A, c = 5.4868(5)A, space group Pnma(62), and R = 0.0484 for 398 observed reflections. The octahedral sites are occupied by Co ions only, while the tetrahedral sites are randomly occupied by Co and Al.; The crystal structure of LaSr{dollar}sb3{dollar}(Fe{dollar}sb{lcub}rm 1-x{rcub}{dollar}Al{dollar}sb{lcub}rm x{rcub})sb3{dollar}O{dollar}sb{lcub}10-delta{rcub}{dollar} phase was determined by single crystal x-ray diffraction and neutron powder diffraction. For the single crystal {dollar}rm LaSrsb3(Fesb{lcub}0.8{rcub}Alsb{lcub}0.2{rcub})sb3Osb{lcub}8.95{rcub}{dollar} phase, tetragonal lattice constants are a = 3.8665(8)A, c = 28.369(8)A, space group I4/mmm, and R = 0.025 for 385 observed reflections. The triple perovskite layers are separated by La/Sr-O rock salt units in agreement with the structure of the {dollar}rm Srsb4Tisb3Osb{lcub}10{rcub}{dollar} phase. The oxygen vacancies occur primarily in the O4 and O2 sites, the equatorial layer of the central octahedron and the bridging atom, respectively. There is a linear relationship between the c-axis dimension and oxygen deficiency.; The crystal structure of two compounds having the generic formula {dollar}rm Lnsb{lcub}4-x{rcub}Asb{lcub}4+x{rcub}Cosb{lcub}2+y{rcub}Alsb{lcub}2-y{rcub}Osb{lcub}15{rcub}{dollar} has been determined. {dollar}rm Ndsb{lcub}3.43{rcub}Basb{lcub}4.42{rcub}Co(Cosb{lcub}1.23{rcub}Alsb{lcub}1.77{rcub})Osb{lcub}15{rcub}{dollar} (Nd compound), hexagonal, P6{dollar}sb3{dollar}mc, a = 11.544(1)A, c = 6.912(1)A, and R = 0.045 for 758 observed reflections. {dollar}rm Ysb2Srsb6Co(Cosb{lcub}1.08{rcub}Alsb{lcub}1.92{rcub})Osb{lcub}15{rcub}{dollar} (Y compound), hexagonal, P6{dollar}sb3{dollar}mc, a = 11.199(2)A, c = 6.664(1), and R = 0.076 for 373 observed reflections. The structure consists of clusters formed by a Co-oxygen octahedron that shares three corners of a triangular face with three separate Co/Al-oxygen tetrahedra leading to a cluster formula {dollar}rm{lcub} Cosp{lcub}VI{rcub}(Co/Al)sb3sp{lcub}IV{rcub}{rcub}Osb{lcub}15{rcub}{dollar}. Two such clusters exist in the unit cell and they are joined by rare earth and alkaline earth cations in 6-fold, 8-fold (bisdisphenoid), 10-fold (capped trigonal prism), and 12-fold (cubic close packing) coordination to the oxygen ions.