Additional Oxygen Ordering in "La2NiO4.25" (La8Ni4O17): I. Electron and Neutron Diffraction Study

✍ Scribed by A. Demourgues; F. Weill; B. Darriet; A. Wattiaux; J.C. Grenier; P. Gravereau; M. Pouchard

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 534 KB
• Volume: 106
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1993.1292

✦ Synopsis

A new material with the composition (\mathrm{La}{2} \mathrm{NiO}{4.25}) exhibiting a large additional oxygen amount with respect to the (\mathrm{K}{2} \mathrm{NiF}{4})-type structure has been prepared using an electrochemical process. A monoclinic unit cell (C-centered) has been determined by TEM. This monoclinic unit cell is four times bigger than the average orthorhombic unit cell and the refined parameters are (a=13.832 \AA, b=10.930 \AA), (c=10.912 \AA, \beta=113.31^{\circ}). The structure has been determined from neutron powder-diffraction data at 300 and (9 \mathrm{~K}). The space group is (C 2). In this space group the site of the additional oxygen atoms is fully occupied. The composition (\mathrm{La}{2} \mathrm{NiO}{4.25}) corresponds to a define compound: (\mathrm{La}{8} \mathrm{Ni}{4} \mathrm{O}_{17}). O 1993 Academic Press, Inc.