Structural characterization and polymorphism of R[sub 2]BaNiO[sub 5] (R = Nd, Gd, Dy, Y, Ho, Er, Tm, Yb) studied by neutron diffraction

Journal Article · Thu Apr 01 00:00:00 EST 1993 · Journal of Solid State Chemistry; (United States)

DOI:https://doi.org/10.1006/jssc.1993.1107· OSTI ID:6050598

Garcia-Matres, E; Rodriguez-Carvajal, J ^[1]; Martinez, J L ^[2]; Alonso, J A ^[3]; Salinas-Sanchez, A; Saez-Puche, R ^[4]

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1. Institut Laue-Langevin, Grenoble (France)
2. Universidad Autonoma de Madrid (Spain)
3. Instituto de Ciencia de Materiales de Madrid (Spain)
4. Universidad Complutense, Madrid (Spain)

The family of compounds R[sub 2]BaNiO[sub 5] (R = Nd, Dy, Y, Ho, Er, Tm, Yb) has been studied by neutron powder diffraction at room temperature. All of them present orthorhombic symmetry (space group Immm, Z = 2). The main feature of these materials is the existence of one-dimensional chains of vertex-sharing NiO[sub 6] octahedra along the a-axis. The present research has revealed the effect of the size of the rare earth ions on the structural parameters, which plays a role nearly equivalent to a hydrostatic [open quotes]chemical pressure[close quotes] in the geometric distortion of the structure. The volume of the Ni and Ba polyhedra varies linearly vs the ionic radius of the rare earth. The overall agreement between the valence bond sums and formal charges is very poor. This fact indicates that the present structure is under very high internal stress and may be metastable. The authors speculate that there may exist a dimorphism in the other members of this family of oxides, similar to that already found for the Tm, Yb, and Lu compounds. 38 refs., 8 figs., 2 tabs.

• OSTI ID: 6050598
• Journal Information: Journal of Solid State Chemistry; (United States), Vol. 103:2; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM OXIDES
CRYSTAL STRUCTURE
NICKEL OXIDES
RARE EARTH COMPOUNDS
YTTRIUM OXIDES
DYSPROSIUM OXIDES
ERBIUM OXIDES
GADOLINIUM OXIDES
HOLMIUM OXIDES
IONS
NEODYMIUM OXIDES
NEUTRON DIFFRACTION
ORTHORHOMBIC LATTICES
SYMMETRY
THULIUM OXIDES
VALENCE
YTTERBIUM OXIDES
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
CHALCOGENIDES
CHARGED PARTICLES
COHERENT SCATTERING
CRYSTAL LATTICES
DIFFRACTION
DYSPROSIUM COMPOUNDS
ERBIUM COMPOUNDS
GADOLINIUM COMPOUNDS
HOLMIUM COMPOUNDS
NEODYMIUM COMPOUNDS
NICKEL COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
SCATTERING
THULIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
YTTERBIUM COMPOUNDS
YTTRIUM COMPOUNDS
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies