Fabrication and Microstructural Development of Ag-Clad TlBa2Ca2Cu3Ox Tapes

(Cu,Tl)Ba2Ca3Cu4Ox compositions: I. The influence of synthesis time and temperature on the phase formation and evaporation$ndash$condensation mechanism

“…In our case, weight loss (see section 3.2) enhances with temperature and time and the same phase formation scenario as in [27,28] can be applied, but instead of double Tl-layer phases at the first reaction stages, we have found the 1212 phase. The reaction path, in which Tl-1212 was used as a precursor for the synthesis of the Tl-1223 phase also has been reported by Biondo et al [29]. Phase 1212 can be in equilibrium with 1223 phase (figure 4(c)) and this result is consistent with the data from [12,13], where the authors pay attention to phase formation using 223-precursors, but contrary to phase diagrams from [9][10][11] in which the 234 composition is investigated.…”

Liquid phase sintering and microstructure development of Ag-clad Tl-1223 superconductor

“…The acoustic velocity results are consistent with kinetic data from Luo et al, who found that 4000 min were necessary for complete conversion to Bi-2223 [7]. The results are also consistent with previous work on the Tl-1223 system that showed that full phase conversion occurred after 30 min [4].…”

“…Mukai et al reduced second phases in Bi-2223 from 30 to 8% with an accompanying increase in J c from 0.5 × 10 4 A cm −2 to 4.7 × 10 4 A cm −2 [3]. Weak-link behaviour is a limitation for powder-in-tube (PIT) Tl-1223 tapes and low J c has been correlated with poor grain alignment and secondary phases [4]. A high J c of 1.9 × 10 4 A cm −2 at 77 K in zero applied field was reported for Tl-1223 PIT tapes; however, these tapes were weak linked and exhibited little grain alignment [5].…”

“…One possible reaction path involves the formation of Tl-2223, which, upon further annealing, decomposes to Tl-1223 [9]. In addition, it has been reported that Tl-1212 is a precursor of Tl-1223 phase formation [4]. The two different reaction paths suggest that Tl 2 O vapour pressure is an important variable in Tl-1223 synthesis.…”