Synthesis and Study of Hg-Based 1222-Type Superconducting Cuprates (Hg, M)Sr2(Ln, Ce)2Cu2Oz

✍ Scribed by E. Kandyel; A. Yamamoto; J.G. Wen; S. Tajima

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 347 KB
• Volume: 154
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2000.8869

✦ Synopsis

A novel series of 991222-type:: copper oxides described by the formula (Hg, M)Sr 2 (Ln, Ce) 2 Cu 2 O z (M ‫؍‬ Ti, V, Cr, Mo, W, Re; and Ln ‫؍‬ Sm, Eu, Gd, Dy, Ho, Er) have been synthesized under high pressure. The structure was determined by combination of X-ray powder di4raction, electron di4raction and high-resolution electron microscopy measurements. The materials are isostructural with (Pb, Cu)-1222, crystallizing in a tetragonal unit cell, space group I4/mmm. The compounds adopt the 1222-type structure with an intergrowth of three types of layers: oxygen-de5cient perovskite (CuO 5 pyramidal layers), double 6uorite-type layers, and double rock-salt layers. A correlation between lattice parameters and e4ective ionic radii of the (Ln, Ce) site is determined for (Hg 0.75 W 0.25 )Sr 2 (Ln 1.5 Ce 0.5 )Cu 2 O z , Ln ‫؍‬ Sm+Er. Except for Cr-containing compound, bulk superconductivity is observed in all the synthesized compounds. The value of T c is related to both the e4ective ionic radius of the (Ln, Ce) site and the valence of the M-element. Among these compounds, the sample with nominal composition of (Hg 0.75 W 0.25 )Sr 2 (Gd 1.5 Ce 0.5 )Cu 2 O z recorded the highest T c up to 75 K.