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

• Published in: Journal of solid state chemistry 2001-02, Vol.156 (2), p.355-363
• Main Authors: Akahoshi, D., Ueda, Y.
• Format: Article
• Language: English
• Subjects: charge order; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Crystalline state (including molecular motions in solids); Crystallographic aspects of phase transformations; pressure effects; Exact sciences and technology; Inorganic compounds; Magnetic phase boundaries (including magnetic transitions, metamagnetism, etc.); Magnetic properties and materials; magnetic transition; Magnetically ordered materials: other intrinsic properties; metal–insulator transition; oxygen nonstoichiometry; phase diagram; phase separation; Physics; structural transition; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; superstructure; Water, oxides, hydroxides, peroxides
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1006/jssc.2000.9006

We synthesized YBaCo2O5+x with various oxygen contents x and investigated physical and structural properties. YBaCo2O5+x can be classified 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 0.50≤x and 0.25≤x≤0.44, 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 0.00≤x≤0.19, YBaCo2O5+x has no longer superstructure. YBaCo2O5+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.