The intermediate phase during (Bi,Pb)2Sr2CaCu2O8+δ to (Bi,Pb)2Sr2Ca2Cu3O10+δ phase transformation

✍ Scribed by Weimin Bian; Yimei Zhu; Y.L. Wang; M. Suenaga

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 490 KB
• Volume: 248
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(95)00240-5

✦ Synopsis

We report our observations on and identification of an intermediate phase, (Bi,Pb)4Sr4CaaCusOls+8 (denoted as Bi/4435), during the phase transformation of (Bi,Pb)2Sr2CaCu2Os+ 8 (Bi/2212) to (Bi,Pb)2Sr2Ca2Cu3010 + 8 (Bi/2223) in powder-in-tube processed tapes. The unit cell of the phase consists of one half each of the Bi/2212 and the Bi/2223 cell, with lattice parameters of a = b = 5.4 A and c = 33.9 A. The space group of the new phase was determined to be Pbmn using the extinction rule of the selected-area electron diffraction, as well as convergent beam electron diffraction and high-resolution electron microscopy. The presence of the Bi/4435 phase and the abundance of its local structure during the early stage of the transformation suggests that the Bi/2223 phase is formed by the rapid insertion of two extra Ca/CuO bi-layers, one at a time, into the two identical CuO/Ca/CuO building blocks of the Bi/2212 matrix. This finding may shed light on the mechanism of structural phase transformation in layered cuprate superconductors.