Phase evolution during the melting and recrystallization of ceramic core in the (Bi,Pb)-2223 tape

J. Y. Li (1, 2) , Jean-Louis Soubeyroux (3) , H.L. Zheng (2) , C.S. Li (2) , Y.F. Lu (2) , Laureline Porcar , Robert Tournier (4) , Lian Zhou (1, 2)

1 NPU - Northwestern Polytechnical University [Xi'an]
2 NIN - Northwest Institute for Nonferrous Metal Research
3 Laboratoire de Cristallographie
4 CRETA - Consortium de Recherches pour l'Emergence des Technologies Avancées

The phase evolution during melting and recrystallization of ceramic core in Ag-sheathed (Bi,Pb)-2223 monofilamentary tape has been studied. The tape was fabricated by PIT process with powders containing nearly pure (Bi,Pb)-2223 phase. Short samples were melted at 805ºC, 808ºC, 812ºC, 816ºC and 831ºC, slowly cooled down at 1.5ºC/hr. and quenched in air at room temperature. X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS) were applied for the phase identification. XRD patterns of samples show that (Bi,Pb)-2223 core is partially melted at 805ºC, 808ºC, 812ºC, and well reformed directly from the melt during the slow cooling. More (Bi,Pb)-2223 phase is decomposed at temperatures higher than 816ºC and can not recrystallize, indicating that a partial melting at some temperatures around a given temperature range is essential for (Bi,Pb)-2223 phase reformation. The results of EDS analysis show that the melt composition moves from that between “2223” and “2212” stoichiometries towards 2212-like stoichiometry with increasing temperature, and Bi-containing 2:1 phase is the main secondary phase. This seems to lead to the conclusion that (Bi,Pb)-2223 phase decomposes incongruently into a 2212-like liquid and (Ca,Sr)-cuprates. 2:1 phase plays the most important role in (Bi,Pb)-2223 melt-recrystallization process. Our results also reveal that plate-like shape (Bi,Pb)-2223 grains can be obtained via melting and recrystallization if the optimum processing conditions are used

Mots clés: (Bi; Pb)-2223 tape; melting and recrystallization; phase evolution

Domaines: Matériaux

J. Y. Li, Jean-Louis Soubeyroux, H.L. Zheng, C.S. Li, Y.F. Lu, et al.. Phase evolution during the melting and recrystallization of ceramic core in the (Bi,Pb)-2223 tape. Physica C: Superconductivity and its Applications, 2006, 450, pp.56-60. ⟨10.1016/j.physc.2006.08.010⟩. ⟨hal-00265002⟩