Structural Disorder in YSr2Cu2CoO7 and Substituted Variants

✍ Scribed by T.G.N. Babu; J.D. Kilgour; P.R. Slater; C. Greaves

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 315 KB
• Volume: 103
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1993.1125

✦ Synopsis

The phase (\mathrm{YSr}{2} \mathrm{Cu}{2} \mathrm{CoO}{7}) (orthorhombic, (/ \mathrm{ma}^{2}) ) is structurally related to (\mathrm{YSr}{2} \mathrm{Cu}{2} \mathrm{GaO}{7}), but has a component of disorder associated with the oxygen sublattice. Substitutions of small amounts of Ba for (\mathrm{Sr}), or (\mathrm{Cu}) for (\mathrm{Co}), have been studied, and shown by powder diffraction methods to increase the level of disorder. (\mathrm{YSr}{1.8} \mathrm{Ba}{0.2} \mathrm{Cu}{2} \mathrm{CoO}{7}) and (\mathrm{YSr}{2} \mathrm{Cu}{2.28} \mathrm{Co}{0.25} \mathrm{O}{7}), for example, have been shown by neutron diffraction to have tetragonal symmetry ( (P 4 / \mathrm{mmm}) ), which appears related to significant displacements of some of the oxygen ions. The nature of the disorder in the parent phase is discussed and compared with the structural observations on substituted derivatives. 1993 Academic Press, Inc.