Evolution of the structure of the K{sub 2}NiF{sub 4} phases La{sub 2{minus}x}Sr{sub x}NiO{sub 4+{delta}} with oxidation state: Octahedral distortion and phase separation (0.2 {le} x {le} 1.0)
- Univ. of Oxford (United Kingdom). Dept. of Chemistry
- National Inst. for Standards and Technology, Gaithersburg, MD (United States). Centre for Neutron Research
The structural properties of the La{sub 2{minus}x}Sr{sub x}NiO{sub 4+{delta}} solid solution have been investigated by high resolution powder neutron diffraction as a function of Sr dopant concentration. There is a significant change in the evolution of the shape of the NiO{sub 6} octahedron beyond x = 0.6, where previous transport measurements have indicated a transition in the electronic structure. For the x = 1 member of the series prepared under conditions often adopted in the literature, a subtle inhomogeneity is visible in the high-resolution powder diffraction patterns and interpreted as arising from a distribution of La/Sr ratios throughout the sample under these widely used preparative conditions. The refined model, incorporating both strain broadening and Bragg peak displacement, can be interpreted as a continuum of phases with differing c, but similar a, lattice parameters. Preparation of LaSrNiO{sub 4+{delta}} at 1450 C appears to overcome this effect but Rietveld refinement is only possible with the aid of hkl dependent line broadening analysis, in contrast to the other members of the series studied.
- OSTI ID:
- 679240
- Journal Information:
- Journal of Solid State Chemistry, Vol. 145, Issue 2; Other Information: PBD: Jul 1999
- Country of Publication:
- United States
- Language:
- English
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