Thermogravimetric study on HgBa2Can−1CunO2(n+1)+δ (n = 1, 2, 3) superconductors at various oxygen partial pressures

✍ Scribed by Ayako Tokiwa-Yamamoto; Atsushi Fukuoka; Makoto Itoh; Seiji Adachi; H Yamauchi; Keiichi Tanabe

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 466 KB
• Volume: 269
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(96)00470-4

✦ Synopsis

The oxygen non-stoichiometry of HgBa2Ca ._ 1Cu,O2(,+ 1)+ 8 (Hg-12(n -1)n, n = 1, 2, 3) superconductors was studied by thermogravimetric analysis (TGA) in a flowing gas atmosphere with various partial pressures of oxygen ranging from 10 -5 to 10 atm. In 1 arm oxygen, irreversible reactions, probably corresponding to vaporization of Hg, were observed above about 420, 480 and 510°C for Hg-1201, 1212 and 1223 samples, respectively. Reversible reactions with oxygen absorption and desorption were confirmed below these temperatures. By controlling the oxygen partial pressure during the heating process up to 300°C and a subsequent cooling process, we obtained Hg-12(n -1)n samples with various oxygen contents. The superconducting properties of these samples were also studied. It was found that the oxygen non-stoichiometry of Hg-12(n -1)n superconductors is very sensitive to the oxidizing atmosphere when they are annealed, even below 300°C.