Oxygen Nonstoichiometry, Structures, and Physical Properties of YBaCo2O5+x (0.00≤x≤0.52)

✍ Scribed by D. Akahoshi; Y. Ueda

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 238 KB
• Volume: 156
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2000.9006

✦ Synopsis

We synthesized YBaCo 2 O 5؉x with various oxygen contents x and investigated physical and structural properties. YBaCo 2 O 5؉x can be classi5ed into three parts of composition region in the structural properties. Two kinds of superstructure, 2 ؋ 1 ؋ 1 and 3 ؋ 3 ؋ 1, originating in the ordering of excess oxygen in Y(O) x layer appear in the range 0.504 4x and 0.254 4x4 40.44, respectively. The 2 ؋ 1 ؋ 1 phase shows the metal+insulator transition accompanied with the large lattice distortion and the magnetic transition. The 3 ؋ 3 ؋ 1 phase (stoichiometric composition, x ‫؍‬ 0.44) also shows some magnetic and structural transitions. A plausible model of the 3 ؋ 3 ؋ 1 superstructure is proposed. In the range 0.004 4x4 40.19, YBaCo 2 O 5؉x has no longer superstructure. YBaCo 2 O 5؉x in x ‫؍‬ 0.00 shows successive phase transitions, a paramagnetic tetragonal to antiferromagnetic orthorhombic transition, and a charge order transition. The present study reveals a simultaneous phase separation with the charge order transition.