High-resolution electron microscope analysis of new type of superconductors in a BaCaCuCO Oxycarbonate system

✍ Scribed by Yoshio Matsui; Tetsuya Kawashima; Eiji Takayama-Muromachi

• Book ID: 103947534
• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 364 KB
• Volume: 235-240
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(94)91339-0

✦ Synopsis

A new homologous series of oxycarbonate superconductors with ideal compositions (Cu0.5C0.5)mBam+lCan_lCunOy, where m=l & 2; n=3, 4 (and 5 for m=2), are prepared in a Ba-Ca-Cu-C-O system under high pressure of around 5 Gpa, and their structures are revealed by HRTEM. Both (Cu,C)-1223 (Tc=67K) and 1234 ( Tc=117K) consist of BaO-[Cu,C]O-BaO blocks sandwiched by Can-l(CuO2)n infinite-layer like blocks. Structures of (Cu,C)-2334 (Tc=113K) and 4679 (2334+2345), on the other hand, consists of thicker blocks of BaO-[Cu,C]O-BaO-[Cu,C]O-BaO, also sandwiched by the Can-l(CuO2)n type blocks. Superstructures with dual periodicity a=2at due to ordering of Cu and C within the [Cu,C]O layers are commonly observed. Anti-phase relations of Cu and C positions along the c-direction are observed in (Cu,C)-1223, 1234 and 2323 phases with c=2ct, while in-phase relations are observed in (Cu,C)-2334 and 4679 (2334+2345) phases with c=ct.