A new model for the formation of high-Tcphase in superconductive (Bi, Pb)2Sr2Ca2Cu3Oxglass-ceramics

✍ Scribed by Jabri Khaled; Takayuki Komatsu; Kazumasa Matusita; Ryuji Sato

• Publisher: Springer US
• Year: 1996
• Tongue: English
• Weight: 457 KB
• Volume: 7
• Category: Article
• ISSN: 0957-4522
• DOI: 10.1007/bf00188952

✦ Synopsis

The formation mechanism of the high-To phase through the glass-ceramic route and the role of Pb on the formation of this phase have been investigated. It was found that a new compound with the chemical composition Pb2Sr3 xCaxCuOv (x = 1.8) precipitates at around 550°C. This phase is stable up to 800°C, where it begins to decompose, and at 850°C it completely disappears. It was found that some part of the released Pb diffuses into the 2212 phase leading to the formation of Pb-containing 2212 phase, (Bi,Pb)2Sr2CaCu2Ox. On the other hand, an endothermic peak, probably arising from the melting of (Bi,Pb)2Sr2CaCu2Ox phase or melting at grain boundaries containing Pb 2+, was observed at 856°C only in Pb-containing samples that were heat treated. The liquid phase attributed to the endothermic peak may enhance the formation of high-Tc phase (2223 phase). The growth kinetics for the high-To phase were analysed using the Johnson-MehI-Avrami equation; the results indicate that the growth of the high-To phase is controlled by a diffusion process and the activation energy for its formation in the initial stage (shorter than 96 h) is 576_+45 kJ tool -1