Crystal Structure and Superconductivity of the Mo-Stabilized Sr-Based YSr2Cu2.7Mo0.3O7-δ Compound

✍ Scribed by S.F. Hu; R.S. Liu; S.C. Su; D.S. Shy; D.A. Jefferson

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 502 KB
• Volume: 112
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1994.1289

✦ Synopsis

The crystal structure of the Mo-stabilized Sr-based superconductor with nominal composition (\mathrm{YSr}{2} \mathrm{Cu}{2.7} \mathrm{Mo}{0.3} \mathrm{O}{7-\delta}) has been analyzed by X-ray powder diffraction (XRD), electron diffraction, and high-resolution electron microscope techniques. The material crystallizes in the space group (P 4 / \mathrm{mmm}), with lattice parameters (a=3.8138(2)) and (c=11.5204(8) \AA). In the structure, the Mo ions are exclusively substituted for copper and are located mainly on the planar coordinated ([\mathrm{Cu}(2)]) sites ( (\sim 24 %), with only a small proportion on the chain ([\mathrm{Cu}(1)]) sites ((\sim 6 %)) in the parent (\mathrm{YBa}{2} \mathrm{Cu}{3} \mathrm{O}{7}) (123-type) structure. A disordering of the hole reservoir layer ([\mathrm{Mo}(1) / \mathrm{Cu}(1)]-\mathrm{O}(3)) due to the displacement of the oxygen ions ([\mathrm{O}(3)]) from their ideal positions of ((0,0.5,0)) to ((0.13,0.5), 0) was found in the XRD refinement, but neither a superlattice nor any form of intergrowth along the (a^{}) and (c^{}) directions was observed by electron diffraction and high-resolution electron microscopy. The chemical substitution of copper by molybdenum renders the (\mathrm{YSr}{2} \mathrm{Cu}{3} \mathrm{O}{7}) compound superconducting, with (T_{\mathrm{c}}) up to 45 K. O 1994 Academic Press, Inc.