Effect of the phase compositions at the final stage of heat treatment on the critical current density in Bi:2223/Ag tapes

Abstract

The effect of the phase compositions after the final stage of heat treatment on the critical current density in Bi:2223/Ag tapes has been investigated. A high volume fraction of Bi:2223 has been considered the most critical factor in achieving a high ; however, it is extremely difficult to attain pure Bi:2223 phase via routine thermomechanical processing. Although a higher volume fraction of Bi:2223 phase can be attained using a higher processing temperature, it is always found to co-exist with Bi:2201 which resides at Bi:2223 colony boundaries. As these possess a plate-like morphology, the Bi:2201 joins weak links in a conductible chain. Bi:2201 can be eliminated using an annealing step at the end of the last thermal cycle, resulting in a significant improvement in . At annealing temperatures below , Bi:2223 decomposes into Bi:3221 and other cuprates, which degrade further. Magnetization, AC susceptibility and resistivity measurement results confirm that the Bi:2201 and Bi:3221 act as weak links.

Effect of the precursor powders on the final properties of hot-forged Bi2223 textured discs

“…But for only 20 h of reaction at 850 • C, the main peaks from the Sr 14 Cu 24 O 41 (or 14, 24) phase are strong. This result confirms conclusions of the paper by Giannini et al [27] in which it is shown that the formation of (14,24) is fast at a high temperature. During the heating step, the (14,24) phase content increases and saturates when the dwell temperature is attained.…”

“…This result confirms conclusions of the paper by Giannini et al [27] in which it is shown that the formation of (14,24) is fast at a high temperature. During the heating step, the (14,24) phase content increases and saturates when the dwell temperature is attained. Maintaining the temperature constant then induces a decrease in (14,24) phase.…”

“…The presence of the Bi2212 phase in the samples textured at 838 • C is also associated with the (Pb,Bi) 3 Sr 2 Ca 2 CuO y (Bi3221) phase. Traces of Bi3221 have been reported in fully reacted Bi2223 compounds by several authors [23][24][25]. In this case, the Bi2223 phase has not been completely formed and secondary phases still coexist with the Bi2223 and Bi2212 phases at lower sintering temperatures.…”

The effects of crystallization on the magnetic properties and critical current in Bi$ndash$Sr$ndash$Ca$ndash$Cu$ndash$O glass$ndash$ceramics

“…Superconducting coupling between superconducting crystalline grain boundaries in the Bi-based ceramics is very weak [3]. The presence of non-superconducting phases (such as Cu 2 O) in the investigated samples and the presence of Bi 3+ , Ca 2+ or Cu 2+ at the grain boundaries can limit weak coupling between superconducting grains [9][10][11]. This could lead to some differences between T c values of the samples and the broadening of the superconducting transition.…”

Photoacoustic Spectra of CdInGaS4 with a DC Electric Field

“…Some of them, commonly listed in the literature, are: grain quality and connectivity (weak links), pinning centres, stoichiometry of the 2223 phase, grain size, etc. The precise stoichiometry of the 2223 phase, as stated by many authors [9,[10][11][12][13], is an essential parameter. Lead is the one of the elements whose loss during sintering has been reported most frequently for tapes [12,13] as well as for bulk samples [14,15].…”