Study of (Bi,Pb)-2223 phase formation in reaction couples

The phase assemblage and particle sizes of precursor powders have been optimized in a sequence for fabricating Ag/BSCCO-2223 composite tapes. Firstly, an optimal calcination temperature was determined based on the experimental results. Then, the precursors calcined at the optimal temperature were ball-milled for different dwell times to obtain varied particle sizes. The effects of both the phase assemblages and particle sizes of the precursor powder on the phase formation, microstructure and transport J c of Bi-2223/Ag tapes have been investigated. The results show that the precursor phase assemblage has a large impact on the reaction routes, microstructure, and J c property. Meanwhile, a fine powder is beneficial for the grain growth, alignment, and J c enhancement in fully reacted tapes. The best J c was achieved in the tape made from the powder after optimizing the phase assemblage and particle size.

Section: Characterizations Of Precursor Powderssupporting

confidence: 91%

Optimization of precursor powders for manufacturing Bi-2223/Ag tapes

Jiang

Yoo

et al. 2002

“…We chose to not exceed 820 • C, in order to avoid the decomposition of Ca 2 PbO 4 (T f = 822 • C) [36] which forms CaO and a liquid phase rich in Pb, because CaO reacts with CuO to form Ca 2 CuO 3 [37], which in turn accelerates the formation of the Bi-2223 phase. Indeed, the initial formation of the Bi-2223 phase occurs around 820 • C [38] and a powder calcined above this temperature generates a great number of Bi-2223 nuclei, thus opposing the growth of the Bi-2223 grains during sintering [39,40] and resulting in the formation of small Bi-2223 grains and, consequently, a weaker J c 2. Characteristic morphologies of the calcined powders are shown in figure 4, and show the large differences in size and morphology according to the selected calcination conditions.…”

Section: Characterization Of Calcined Powdersmentioning

confidence: 99%

Optimization of calcination conditions on the Bi-2223 kinetic formation and grain size

Garnier¹,

Monot²,

Desgardin³

2000

The effects of the calcination conditions (time, temperature, intermediate milling) on the kinetics of formation of Bi-2223 and on the grain size were studied using a powder precursor synthesized by the polymer matrix method. The samples were characterized by XRD and SEM analysis. The grain size and the kinetics of formation of Bi-2223 strongly depend on the calcination conditions and thus on the phase assemblages formed at the end of the calcination that determines the reactivity during sintering. The higher the calcination temperature is the larger the grain size. We have observed that 24 h of calcination at 820 °C without intermediate milling allows one to obtain 79% of Bi-2223 phase in 60 h of sintering at 835 °C.

“…(Bi, Pb) 2 Sr 2 Ca 2 Cu 3 O 10+δ ((Bi, Pb)2223) is well-known as a high T C superconducting material and so much effort has been made to improve the critical current density (J c ) of Agsheathed (Bi, Pb)2223 tapes. Detailed knowledge on the (Bi, Pb)2223 phase formation is necessary for the development of Ag-sheathed (Bi, Pb)2223 tapes and many research results have been published over the past few years [1][2][3][4][5][6][7]. In (Bi, Pb)2223 phase transformation, Bi 2 Sr 2 CaCu 2 O 8 (Bi2212) contained in the precursor are partially melted with secondary phases and a liquid phase forms in the early stages of the sintering process [8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

In situobservation of 2212 intergrowths in the early stages of (Bi, Pb)2223 phase formation using the synchrotron XRD technique

Nakao

Osamura

2005

2212 intergrowths in the (Bi, Pb)2223 phase have been investigated using in situ high temperature synchrotron XRD technique. With a high energy synchrotron x-ray and high resolution diffractometer, we could obtain high resolution powder XRD patterns of (Bi, Pb)2223 and (Bi, Pb)2212 from the whole bulk inside the Ag-sheath. This gave us more detailed information on 2212 intergrowths in the (Bi, Pb)2223 phase than ever before. During in situ observation, the Ag-tubed precursor was kept at 1095 K with flowing Ar-7.8% O 2 mixed gas. The profiles of the diffraction peaks were analysed by Rietveld analysis to evaluate the isotropic and anisotropic lattice strain of (Bi, Pb)2223 and (Bi, Pb)2212. Considering the evolution of anisotropic lattice strain during the heat treatment, it was concluded that 2212 intergrowths in the (Bi, Pb)2223 phase are not in the untransformed region of (Bi, Pb)2212 after incommensurate intercalation, but a stacking fault-like defect contained in the (Bi, Pb)2223 phase during its nucleation and growth. A new model of 2212 intergrowth formation in the (Bi, Pb)2223 phase was suggested and discussed.