**Acknowledgments**

192 Superconductors – Materials, Properties and Applications

Short and long lengths of Bi2212 conductors obtained from pre-reacted powders of Bi2212 were textured using the same thermal cycle with a maximal annealing temperature a little larger than Tm and a relatively small annealing time. This thermal cycle is to be compared to the usual long annealing time imposed at lower temperatures in order to form the superconducting phase from non-reacted precursors. This process is successful even without magnetic field because the melt already contains surviving nuclei of this phase acting as growth nuclei inside the silver-sheathed filaments having a section sufficiently small to accommodate the platelets obtained after growth. The alignment of these platelets and consequently the superconducting critical current are improved by using a dynamic process reproducing the

We have used a model which predicts glass-forming melt properties without using adjustable parameters and only knowing the fusion heat of a bulk multicomponent material, its molar volume, its melting temperature and its vitreous transition temperature Tg. The Bi2212 and Bi2223 ceramics are known to lead to a vitreous state after quenching. The knowledge of Tg leads to the homogeneous nucleation temperature of crystal and to the energy saving associated with the complementary Laplace pressure acting on a critical radius crystal which is associated with the Fermi energies equalization of this crystal and melt at all temperatures T larger than Tg. The melting temperature of each nucleus above Tm depends on its radius which is smaller than its critical value at Tm. A simple method of quantification is used to determine the complementary Laplace pressure depending on the crystal radius. This energy saving of surviving crystals is calculated assuming that the equalization of Fermi energies between crystal and melt virtually occurs by free electron transfer from crystal to melt. A bound state of a s-state electron would be produced in the electrostatic spherical potential of radius Rnm; the energy saving depending on Rnm would be equal to its first energy level. This energy is constant above Tm at constant radius and decreases with θ2 = (T-Tm)2/Tm2 below Tm. The transient and steady-state nucleation times of the Bi2212 nano-crystallized state are predicted in agreement with the observed values. There is a limitation to the model since we consider all atoms to be identical. Consequently, it cannot describe the behaviour at too high temperatures of clusters which have a composition strongly different from that of the melt. The model predicts that the highest melting temperature of surviving crystals occurs at θ = 0.93. This value is too high because the vitreous state is obtained by quenching the melt from θ ≅ 0.3. In addition, Bi2212 and, Bi2223 nuclei are rapidly transformed in secondary phase clusters which govern the nanocrystallization of the melt. We did not find any publication about the existence of a vitreous state of YBCO. This could be due to a much smaller viscosity of this melt. Nevertheless, this material can be magnetically textured due to the presence of intrinsic clusters above Tm. Its unknown energy saving coefficient εls0 could be smaller than 1 and could not be determined

thermal cycle presented above where the wire moves through the magnetic field.

using equations only governing fragile glass-forming melts.

Laureline Porcar, Patricia de Rango, Daniel Bourgault and Robert Tournier

*Institut Néel/CRETA/CNRS/ University Joseph Fourier/Grenoble/France* 

**Author details** 

The authors thank the Institute of Physics Publishing, IOP publishing, Taylor and Francis Group Journals, Elsevier for giving the authorization to reproduce Figure 1 and 2 as published in [16], Figure 4 as published in [23], Figure 6 as published in [26], Figure 7 as published in [34], Figure 8 and 9 as published in [35] and Figure 10 as published in [38].
