New high-Tc superconductor families of Ag1−xCuxBa2Can−1CunO2n+3−y and CuBa2Can−1CunO2n+4−y with Tc>116 K

✍ Scribed by Hideo Ihara; Kazuyasu Tokiwa; Akira Iyo; Masayuki Hirabayashi; Norio Terada; Madoka Tokumoto; Young Seok Song

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 312 KB
• Volume: 235-240
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(94)91715-9

✦ Synopsis

New high-temperature and nontoxic superconductor families of Ag 1-xCuxBa2Can-lCunO2n+3-y witl~ Tc = 117 K and CuBa2Can-lCunO2n+4-y with Tc =116 K were discovered. These materials were prepared by the highpressure technique. The highest Tc was obtained for n=4 i.e. Agl-xCuxBa2Ca3Cu4Oll.y (Ag-1234) and CuBa2Ca3Cu4012_y (Cu-1234) phases. Their structures were analyzed as a tetragonal structure for simplicity. The Ag-1234 phase has the lattice parameters of a=3.8635 A and c= 18.111 A, while the lattice parameters of the Cu-1234 phase are a = 3.8557 A and c= 17.993 A. The Ag-based superconductors have higher Tc and larger lattice parameters than the Cu-based for n=3, 4, and 5. The relationships between the lattice parameter c and the number of CuO2 layers r are c= 8.5 + 3.2(n-1) (A) and c= 8.4 + 3.2(n-1) (A) for Ag and Cu-based superconductors, respectively. The sm,ll CuO2-block spacing (8.5 and 8.4 A) of these families suggests a lowcr anisotropic superconductivity than Hg-and Tl-based superconductor families. The occupation of Ag sites was analyzed.