Atomic redistribution and mass transport in the formation of Bi1.80Pb0.43Sr1.71Ca2.14Cu3O10+x

✍ Scribed by M.G. Smith; D.S. Phillips; D.E. Peterson; J.O. Willis

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 872 KB
• Volume: 224
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(94)90618-1

✦ Synopsis

A sample of nominal BiLsoPbo.43SrL71Ca2a4Cu3Om+x (Bi-2223) composition consisting primarily of fine grains of Bi2Sr2CaCu2Os+x (Bi-2212 ) and CazPbO4 was synthesized under pure oxygen by a solid-state reaction. This assemblage was then convened to large grains of the 110 K superconducting Bi-2223 phase by annealing at 860°C in air. Utilizing scanning electron microscopy and wavelength dispersive X-ray spectroscopy we show that a redistribution of Ca and Pb occurs throughout the matrix during the formation of Bi-2223. These results indicate that the driving force for Pb doped Bi-2223 formation may be due to the large change in entropy caused by melting of one or more of the precursor phases and mixing of the liquid constituents. Melting may be driven by the dependence of the conversion pb4+~-+Pb 2+ on the oxygen partial pressure, with Pb 4+ in Ca2PbO4 and Pb 2+ in the Bi-2223 phase.